Imported Upstream version 1.4upstream/1.4

1 files changed, 1248 insertions, 0 deletions

diff --git a/src/time/format.go b/src/time/format.go
new file mode 100644
index 000000000..04e79f32d
--- /dev/null
+++ b/src/time/format.go
@@ -0,0 +1,1248 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package time
+
+import "errors"
+
+// These are predefined layouts for use in Time.Format and Time.Parse.
+// The reference time used in the layouts is the specific time:
+//	Mon Jan 2 15:04:05 MST 2006
+// which is Unix time 1136239445. Since MST is GMT-0700,
+// the reference time can be thought of as
+//	01/02 03:04:05PM '06 -0700
+// To define your own format, write down what the reference time would look
+// like formatted your way; see the values of constants like ANSIC,
+// StampMicro or Kitchen for examples. The model is to demonstrate what the
+// reference time looks like so that the Format and Parse methods can apply
+// the same transformation to a general time value.
+//
+// Within the format string, an underscore _ represents a space that may be
+// replaced by a digit if the following number (a day) has two digits; for
+// compatibility with fixed-width Unix time formats.
+//
+// A decimal point followed by one or more zeros represents a fractional
+// second, printed to the given number of decimal places.  A decimal point
+// followed by one or more nines represents a fractional second, printed to
+// the given number of decimal places, with trailing zeros removed.
+// When parsing (only), the input may contain a fractional second
+// field immediately after the seconds field, even if the layout does not
+// signify its presence. In that case a decimal point followed by a maximal
+// series of digits is parsed as a fractional second.
+//
+// Numeric time zone offsets format as follows:
+//	-0700  ±hhmm
+//	-07:00 ±hh:mm
+// Replacing the sign in the format with a Z triggers
+// the ISO 8601 behavior of printing Z instead of an
+// offset for the UTC zone.  Thus:
+//	Z0700  Z or ±hhmm
+//	Z07:00 Z or ±hh:mm
+const (
+	ANSIC       = "Mon Jan _2 15:04:05 2006"
+	UnixDate    = "Mon Jan _2 15:04:05 MST 2006"
+	RubyDate    = "Mon Jan 02 15:04:05 -0700 2006"
+	RFC822      = "02 Jan 06 15:04 MST"
+	RFC822Z     = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone
+	RFC850      = "Monday, 02-Jan-06 15:04:05 MST"
+	RFC1123     = "Mon, 02 Jan 2006 15:04:05 MST"
+	RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone
+	RFC3339     = "2006-01-02T15:04:05Z07:00"
+	RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"
+	Kitchen     = "3:04PM"
+	// Handy time stamps.
+	Stamp      = "Jan _2 15:04:05"
+	StampMilli = "Jan _2 15:04:05.000"
+	StampMicro = "Jan _2 15:04:05.000000"
+	StampNano  = "Jan _2 15:04:05.000000000"
+)
+
+const (
+	_                        = iota
+	stdLongMonth             = iota + stdNeedDate  // "January"
+	stdMonth                                       // "Jan"
+	stdNumMonth                                    // "1"
+	stdZeroMonth                                   // "01"
+	stdLongWeekDay                                 // "Monday"
+	stdWeekDay                                     // "Mon"
+	stdDay                                         // "2"
+	stdUnderDay                                    // "_2"
+	stdZeroDay                                     // "02"
+	stdHour                  = iota + stdNeedClock // "15"
+	stdHour12                                      // "3"
+	stdZeroHour12                                  // "03"
+	stdMinute                                      // "4"
+	stdZeroMinute                                  // "04"
+	stdSecond                                      // "5"
+	stdZeroSecond                                  // "05"
+	stdLongYear              = iota + stdNeedDate  // "2006"
+	stdYear                                        // "06"
+	stdPM                    = iota + stdNeedClock // "PM"
+	stdpm                                          // "pm"
+	stdTZ                    = iota                // "MST"
+	stdISO8601TZ                                   // "Z0700"  // prints Z for UTC
+	stdISO8601SecondsTZ                            // "Z070000"
+	stdISO8601ColonTZ                              // "Z07:00" // prints Z for UTC
+	stdISO8601ColonSecondsTZ                       // "Z07:00:00"
+	stdNumTZ                                       // "-0700"  // always numeric
+	stdNumSecondsTz                                // "-070000"
+	stdNumShortTZ                                  // "-07"    // always numeric
+	stdNumColonTZ                                  // "-07:00" // always numeric
+	stdNumColonSecondsTZ                           // "-07:00:00"
+	stdFracSecond0                                 // ".0", ".00", ... , trailing zeros included
+	stdFracSecond9                                 // ".9", ".99", ..., trailing zeros omitted
+
+	stdNeedDate  = 1 << 8             // need month, day, year
+	stdNeedClock = 2 << 8             // need hour, minute, second
+	stdArgShift  = 16                 // extra argument in high bits, above low stdArgShift
+	stdMask      = 1<<stdArgShift - 1 // mask out argument
+)
+
+// std0x records the std values for "01", "02", ..., "06".
+var std0x = [...]int{stdZeroMonth, stdZeroDay, stdZeroHour12, stdZeroMinute, stdZeroSecond, stdYear}
+
+// startsWithLowerCase reports whether the string has a lower-case letter at the beginning.
+// Its purpose is to prevent matching strings like "Month" when looking for "Mon".
+func startsWithLowerCase(str string) bool {
+	if len(str) == 0 {
+		return false
+	}
+	c := str[0]
+	return 'a' <= c && c <= 'z'
+}
+
+// nextStdChunk finds the first occurrence of a std string in
+// layout and returns the text before, the std string, and the text after.
+func nextStdChunk(layout string) (prefix string, std int, suffix string) {
+	for i := 0; i < len(layout); i++ {
+		switch c := int(layout[i]); c {
+		case 'J': // January, Jan
+			if len(layout) >= i+3 && layout[i:i+3] == "Jan" {
+				if len(layout) >= i+7 && layout[i:i+7] == "January" {
+					return layout[0:i], stdLongMonth, layout[i+7:]
+				}
+				if !startsWithLowerCase(layout[i+3:]) {
+					return layout[0:i], stdMonth, layout[i+3:]
+				}
+			}
+
+		case 'M': // Monday, Mon, MST
+			if len(layout) >= i+3 {
+				if layout[i:i+3] == "Mon" {
+					if len(layout) >= i+6 && layout[i:i+6] == "Monday" {
+						return layout[0:i], stdLongWeekDay, layout[i+6:]
+					}
+					if !startsWithLowerCase(layout[i+3:]) {
+						return layout[0:i], stdWeekDay, layout[i+3:]
+					}
+				}
+				if layout[i:i+3] == "MST" {
+					return layout[0:i], stdTZ, layout[i+3:]
+				}
+			}
+
+		case '0': // 01, 02, 03, 04, 05, 06
+			if len(layout) >= i+2 && '1' <= layout[i+1] && layout[i+1] <= '6' {
+				return layout[0:i], std0x[layout[i+1]-'1'], layout[i+2:]
+			}
+
+		case '1': // 15, 1
+			if len(layout) >= i+2 && layout[i+1] == '5' {
+				return layout[0:i], stdHour, layout[i+2:]
+			}
+			return layout[0:i], stdNumMonth, layout[i+1:]
+
+		case '2': // 2006, 2
+			if len(layout) >= i+4 && layout[i:i+4] == "2006" {
+				return layout[0:i], stdLongYear, layout[i+4:]
+			}
+			return layout[0:i], stdDay, layout[i+1:]
+
+		case '_': // _2
+			if len(layout) >= i+2 && layout[i+1] == '2' {
+				return layout[0:i], stdUnderDay, layout[i+2:]
+			}
+
+		case '3':
+			return layout[0:i], stdHour12, layout[i+1:]
+
+		case '4':
+			return layout[0:i], stdMinute, layout[i+1:]
+
+		case '5':
+			return layout[0:i], stdSecond, layout[i+1:]
+
+		case 'P': // PM
+			if len(layout) >= i+2 && layout[i+1] == 'M' {
+				return layout[0:i], stdPM, layout[i+2:]
+			}
+
+		case 'p': // pm
+			if len(layout) >= i+2 && layout[i+1] == 'm' {
+				return layout[0:i], stdpm, layout[i+2:]
+			}
+
+		case '-': // -070000, -07:00:00, -0700, -07:00, -07
+			if len(layout) >= i+7 && layout[i:i+7] == "-070000" {
+				return layout[0:i], stdNumSecondsTz, layout[i+7:]
+			}
+			if len(layout) >= i+9 && layout[i:i+9] == "-07:00:00" {
+				return layout[0:i], stdNumColonSecondsTZ, layout[i+9:]
+			}
+			if len(layout) >= i+5 && layout[i:i+5] == "-0700" {
+				return layout[0:i], stdNumTZ, layout[i+5:]
+			}
+			if len(layout) >= i+6 && layout[i:i+6] == "-07:00" {
+				return layout[0:i], stdNumColonTZ, layout[i+6:]
+			}
+			if len(layout) >= i+3 && layout[i:i+3] == "-07" {
+				return layout[0:i], stdNumShortTZ, layout[i+3:]
+			}
+
+		case 'Z': // Z070000, Z07:00:00, Z0700, Z07:00,
+			if len(layout) >= i+7 && layout[i:i+7] == "Z070000" {
+				return layout[0:i], stdISO8601SecondsTZ, layout[i+7:]
+			}
+			if len(layout) >= i+9 && layout[i:i+9] == "Z07:00:00" {
+				return layout[0:i], stdISO8601ColonSecondsTZ, layout[i+9:]
+			}
+			if len(layout) >= i+5 && layout[i:i+5] == "Z0700" {
+				return layout[0:i], stdISO8601TZ, layout[i+5:]
+			}
+			if len(layout) >= i+6 && layout[i:i+6] == "Z07:00" {
+				return layout[0:i], stdISO8601ColonTZ, layout[i+6:]
+			}
+
+		case '.': // .000 or .999 - repeated digits for fractional seconds.
+			if i+1 < len(layout) && (layout[i+1] == '0' || layout[i+1] == '9') {
+				ch := layout[i+1]
+				j := i + 1
+				for j < len(layout) && layout[j] == ch {
+					j++
+				}
+				// String of digits must end here - only fractional second is all digits.
+				if !isDigit(layout, j) {
+					std := stdFracSecond0
+					if layout[i+1] == '9' {
+						std = stdFracSecond9
+					}
+					std |= (j - (i + 1)) << stdArgShift
+					return layout[0:i], std, layout[j:]
+				}
+			}
+		}
+	}
+	return layout, 0, ""
+}
+
+var longDayNames = []string{
+	"Sunday",
+	"Monday",
+	"Tuesday",
+	"Wednesday",
+	"Thursday",
+	"Friday",
+	"Saturday",
+}
+
+var shortDayNames = []string{
+	"Sun",
+	"Mon",
+	"Tue",
+	"Wed",
+	"Thu",
+	"Fri",
+	"Sat",
+}
+
+var shortMonthNames = []string{
+	"---",
+	"Jan",
+	"Feb",
+	"Mar",
+	"Apr",
+	"May",
+	"Jun",
+	"Jul",
+	"Aug",
+	"Sep",
+	"Oct",
+	"Nov",
+	"Dec",
+}
+
+var longMonthNames = []string{
+	"---",
+	"January",
+	"February",
+	"March",
+	"April",
+	"May",
+	"June",
+	"July",
+	"August",
+	"September",
+	"October",
+	"November",
+	"December",
+}
+
+// match returns true if s1 and s2 match ignoring case.
+// It is assumed s1 and s2 are the same length.
+func match(s1, s2 string) bool {
+	for i := 0; i < len(s1); i++ {
+		c1 := s1[i]
+		c2 := s2[i]
+		if c1 != c2 {
+			// Switch to lower-case; 'a'-'A' is known to be a single bit.
+			c1 |= 'a' - 'A'
+			c2 |= 'a' - 'A'
+			if c1 != c2 || c1 < 'a' || c1 > 'z' {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func lookup(tab []string, val string) (int, string, error) {
+	for i, v := range tab {
+		if len(val) >= len(v) && match(val[0:len(v)], v) {
+			return i, val[len(v):], nil
+		}
+	}
+	return -1, val, errBad
+}
+
+// appendUint appends the decimal form of x to b and returns the result.
+// If x is a single-digit number and pad != 0, appendUint inserts the pad byte
+// before the digit.
+// Duplicates functionality in strconv, but avoids dependency.
+func appendUint(b []byte, x uint, pad byte) []byte {
+	if x < 10 {
+		if pad != 0 {
+			b = append(b, pad)
+		}
+		return append(b, byte('0'+x))
+	}
+	if x < 100 {
+		b = append(b, byte('0'+x/10))
+		b = append(b, byte('0'+x%10))
+		return b
+	}
+
+	var buf [32]byte
+	n := len(buf)
+	if x == 0 {
+		return append(b, '0')
+	}
+	for x >= 10 {
+		n--
+		buf[n] = byte(x%10 + '0')
+		x /= 10
+	}
+	n--
+	buf[n] = byte(x + '0')
+	return append(b, buf[n:]...)
+}
+
+// Never printed, just needs to be non-nil for return by atoi.
+var atoiError = errors.New("time: invalid number")
+
+// Duplicates functionality in strconv, but avoids dependency.
+func atoi(s string) (x int, err error) {
+	neg := false
+	if s != "" && (s[0] == '-' || s[0] == '+') {
+		neg = s[0] == '-'
+		s = s[1:]
+	}
+	q, rem, err := leadingInt(s)
+	x = int(q)
+	if err != nil || rem != "" {
+		return 0, atoiError
+	}
+	if neg {
+		x = -x
+	}
+	return x, nil
+}
+
+// formatNano appends a fractional second, as nanoseconds, to b
+// and returns the result.
+func formatNano(b []byte, nanosec uint, n int, trim bool) []byte {
+	u := nanosec
+	var buf [9]byte
+	for start := len(buf); start > 0; {
+		start--
+		buf[start] = byte(u%10 + '0')
+		u /= 10
+	}
+
+	if n > 9 {
+		n = 9
+	}
+	if trim {
+		for n > 0 && buf[n-1] == '0' {
+			n--
+		}
+		if n == 0 {
+			return b
+		}
+	}
+	b = append(b, '.')
+	return append(b, buf[:n]...)
+}
+
+// String returns the time formatted using the format string
+//	"2006-01-02 15:04:05.999999999 -0700 MST"
+func (t Time) String() string {
+	return t.Format("2006-01-02 15:04:05.999999999 -0700 MST")
+}
+
+// Format returns a textual representation of the time value formatted
+// according to layout, which defines the format by showing how the reference
+// time, defined to be
+//	Mon Jan 2 15:04:05 -0700 MST 2006
+// would be displayed if it were the value; it serves as an example of the
+// desired output. The same display rules will then be applied to the time
+// value.
+// Predefined layouts ANSIC, UnixDate, RFC3339 and others describe standard
+// and convenient representations of the reference time. For more information
+// about the formats and the definition of the reference time, see the
+// documentation for ANSIC and the other constants defined by this package.
+func (t Time) Format(layout string) string {
+	var (
+		name, offset, abs = t.locabs()
+
+		year  int = -1
+		month Month
+		day   int
+		hour  int = -1
+		min   int
+		sec   int
+
+		b   []byte
+		buf [64]byte
+	)
+	max := len(layout) + 10
+	if max <= len(buf) {
+		b = buf[:0]
+	} else {
+		b = make([]byte, 0, max)
+	}
+	// Each iteration generates one std value.
+	for layout != "" {
+		prefix, std, suffix := nextStdChunk(layout)
+		if prefix != "" {
+			b = append(b, prefix...)
+		}
+		if std == 0 {
+			break
+		}
+		layout = suffix
+
+		// Compute year, month, day if needed.
+		if year < 0 && std&stdNeedDate != 0 {
+			year, month, day, _ = absDate(abs, true)
+		}
+
+		// Compute hour, minute, second if needed.
+		if hour < 0 && std&stdNeedClock != 0 {
+			hour, min, sec = absClock(abs)
+		}
+
+		switch std & stdMask {
+		case stdYear:
+			y := year
+			if y < 0 {
+				y = -y
+			}
+			b = appendUint(b, uint(y%100), '0')
+		case stdLongYear:
+			// Pad year to at least 4 digits.
+			y := year
+			switch {
+			case year <= -1000:
+				b = append(b, '-')
+				y = -y
+			case year <= -100:
+				b = append(b, "-0"...)
+				y = -y
+			case year <= -10:
+				b = append(b, "-00"...)
+				y = -y
+			case year < 0:
+				b = append(b, "-000"...)
+				y = -y
+			case year < 10:
+				b = append(b, "000"...)
+			case year < 100:
+				b = append(b, "00"...)
+			case year < 1000:
+				b = append(b, '0')
+			}
+			b = appendUint(b, uint(y), 0)
+		case stdMonth:
+			b = append(b, month.String()[:3]...)
+		case stdLongMonth:
+			m := month.String()
+			b = append(b, m...)
+		case stdNumMonth:
+			b = appendUint(b, uint(month), 0)
+		case stdZeroMonth:
+			b = appendUint(b, uint(month), '0')
+		case stdWeekDay:
+			b = append(b, absWeekday(abs).String()[:3]...)
+		case stdLongWeekDay:
+			s := absWeekday(abs).String()
+			b = append(b, s...)
+		case stdDay:
+			b = appendUint(b, uint(day), 0)
+		case stdUnderDay:
+			b = appendUint(b, uint(day), ' ')
+		case stdZeroDay:
+			b = appendUint(b, uint(day), '0')
+		case stdHour:
+			b = appendUint(b, uint(hour), '0')
+		case stdHour12:
+			// Noon is 12PM, midnight is 12AM.
+			hr := hour % 12
+			if hr == 0 {
+				hr = 12
+			}
+			b = appendUint(b, uint(hr), 0)
+		case stdZeroHour12:
+			// Noon is 12PM, midnight is 12AM.
+			hr := hour % 12
+			if hr == 0 {
+				hr = 12
+			}
+			b = appendUint(b, uint(hr), '0')
+		case stdMinute:
+			b = appendUint(b, uint(min), 0)
+		case stdZeroMinute:
+			b = appendUint(b, uint(min), '0')
+		case stdSecond:
+			b = appendUint(b, uint(sec), 0)
+		case stdZeroSecond:
+			b = appendUint(b, uint(sec), '0')
+		case stdPM:
+			if hour >= 12 {
+				b = append(b, "PM"...)
+			} else {
+				b = append(b, "AM"...)
+			}
+		case stdpm:
+			if hour >= 12 {
+				b = append(b, "pm"...)
+			} else {
+				b = append(b, "am"...)
+			}
+		case stdISO8601TZ, stdISO8601ColonTZ, stdISO8601SecondsTZ, stdISO8601ColonSecondsTZ, stdNumTZ, stdNumColonTZ, stdNumSecondsTz, stdNumColonSecondsTZ:
+			// Ugly special case.  We cheat and take the "Z" variants
+			// to mean "the time zone as formatted for ISO 8601".
+			if offset == 0 && (std == stdISO8601TZ || std == stdISO8601ColonTZ || std == stdISO8601SecondsTZ || std == stdISO8601ColonSecondsTZ) {
+				b = append(b, 'Z')
+				break
+			}
+			zone := offset / 60 // convert to minutes
+			absoffset := offset
+			if zone < 0 {
+				b = append(b, '-')
+				zone = -zone
+				absoffset = -absoffset
+			} else {
+				b = append(b, '+')
+			}
+			b = appendUint(b, uint(zone/60), '0')
+			if std == stdISO8601ColonTZ || std == stdNumColonTZ || std == stdISO8601ColonSecondsTZ || std == stdNumColonSecondsTZ {
+				b = append(b, ':')
+			}
+			b = appendUint(b, uint(zone%60), '0')
+
+			// append seconds if appropriate
+			if std == stdISO8601SecondsTZ || std == stdNumSecondsTz || std == stdNumColonSecondsTZ || std == stdISO8601ColonSecondsTZ {
+				if std == stdNumColonSecondsTZ || std == stdISO8601ColonSecondsTZ {
+					b = append(b, ':')
+				}
+				b = appendUint(b, uint(absoffset%60), '0')
+			}
+
+		case stdTZ:
+			if name != "" {
+				b = append(b, name...)
+				break
+			}
+			// No time zone known for this time, but we must print one.
+			// Use the -0700 format.
+			zone := offset / 60 // convert to minutes
+			if zone < 0 {
+				b = append(b, '-')
+				zone = -zone
+			} else {
+				b = append(b, '+')
+			}
+			b = appendUint(b, uint(zone/60), '0')
+			b = appendUint(b, uint(zone%60), '0')
+		case stdFracSecond0, stdFracSecond9:
+			b = formatNano(b, uint(t.Nanosecond()), std>>stdArgShift, std&stdMask == stdFracSecond9)
+		}
+	}
+	return string(b)
+}
+
+var errBad = errors.New("bad value for field") // placeholder not passed to user
+
+// ParseError describes a problem parsing a time string.
+type ParseError struct {
+	Layout     string
+	Value      string
+	LayoutElem string
+	ValueElem  string
+	Message    string
+}
+
+func quote(s string) string {
+	return "\"" + s + "\""
+}
+
+// Error returns the string representation of a ParseError.
+func (e *ParseError) Error() string {
+	if e.Message == "" {
+		return "parsing time " +
+			quote(e.Value) + " as " +
+			quote(e.Layout) + ": cannot parse " +
+			quote(e.ValueElem) + " as " +
+			quote(e.LayoutElem)
+	}
+	return "parsing time " +
+		quote(e.Value) + e.Message
+}
+
+// isDigit returns true if s[i] is a decimal digit, false if not or
+// if s[i] is out of range.
+func isDigit(s string, i int) bool {
+	if len(s) <= i {
+		return false
+	}
+	c := s[i]
+	return '0' <= c && c <= '9'
+}
+
+// getnum parses s[0:1] or s[0:2] (fixed forces the latter)
+// as a decimal integer and returns the integer and the
+// remainder of the string.
+func getnum(s string, fixed bool) (int, string, error) {
+	if !isDigit(s, 0) {
+		return 0, s, errBad
+	}
+	if !isDigit(s, 1) {
+		if fixed {
+			return 0, s, errBad
+		}
+		return int(s[0] - '0'), s[1:], nil
+	}
+	return int(s[0]-'0')*10 + int(s[1]-'0'), s[2:], nil
+}
+
+func cutspace(s string) string {
+	for len(s) > 0 && s[0] == ' ' {
+		s = s[1:]
+	}
+	return s
+}
+
+// skip removes the given prefix from value,
+// treating runs of space characters as equivalent.
+func skip(value, prefix string) (string, error) {
+	for len(prefix) > 0 {
+		if prefix[0] == ' ' {
+			if len(value) > 0 && value[0] != ' ' {
+				return value, errBad
+			}
+			prefix = cutspace(prefix)
+			value = cutspace(value)
+			continue
+		}
+		if len(value) == 0 || value[0] != prefix[0] {
+			return value, errBad
+		}
+		prefix = prefix[1:]
+		value = value[1:]
+	}
+	return value, nil
+}
+
+// Parse parses a formatted string and returns the time value it represents.
+// The layout  defines the format by showing how the reference time,
+// defined to be
+//	Mon Jan 2 15:04:05 -0700 MST 2006
+// would be interpreted if it were the value; it serves as an example of
+// the input format. The same interpretation will then be made to the
+// input string.
+// Predefined layouts ANSIC, UnixDate, RFC3339 and others describe standard
+// and convenient representations of the reference time. For more information
+// about the formats and the definition of the reference time, see the
+// documentation for ANSIC and the other constants defined by this package.
+//
+// Elements omitted from the value are assumed to be zero or, when
+// zero is impossible, one, so parsing "3:04pm" returns the time
+// corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is
+// 0, this time is before the zero Time).
+// Years must be in the range 0000..9999. The day of the week is checked
+// for syntax but it is otherwise ignored.
+//
+// In the absence of a time zone indicator, Parse returns a time in UTC.
+//
+// When parsing a time with a zone offset like -0700, if the offset corresponds
+// to a time zone used by the current location (Local), then Parse uses that
+// location and zone in the returned time. Otherwise it records the time as
+// being in a fabricated location with time fixed at the given zone offset.
+//
+// When parsing a time with a zone abbreviation like MST, if the zone abbreviation
+// has a defined offset in the current location, then that offset is used.
+// The zone abbreviation "UTC" is recognized as UTC regardless of location.
+// If the zone abbreviation is unknown, Parse records the time as being
+// in a fabricated location with the given zone abbreviation and a zero offset.
+// This choice means that such a time can be parsed and reformatted with the
+// same layout losslessly, but the exact instant used in the representation will
+// differ by the actual zone offset. To avoid such problems, prefer time layouts
+// that use a numeric zone offset, or use ParseInLocation.
+func Parse(layout, value string) (Time, error) {
+	return parse(layout, value, UTC, Local)
+}
+
+// ParseInLocation is like Parse but differs in two important ways.
+// First, in the absence of time zone information, Parse interprets a time as UTC;
+// ParseInLocation interprets the time as in the given location.
+// Second, when given a zone offset or abbreviation, Parse tries to match it
+// against the Local location; ParseInLocation uses the given location.
+func ParseInLocation(layout, value string, loc *Location) (Time, error) {
+	return parse(layout, value, loc, loc)
+}
+
+func parse(layout, value string, defaultLocation, local *Location) (Time, error) {
+	alayout, avalue := layout, value
+	rangeErrString := "" // set if a value is out of range
+	amSet := false       // do we need to subtract 12 from the hour for midnight?
+	pmSet := false       // do we need to add 12 to the hour?
+
+	// Time being constructed.
+	var (
+		year       int
+		month      int = 1 // January
+		day        int = 1
+		hour       int
+		min        int
+		sec        int
+		nsec       int
+		z          *Location
+		zoneOffset int = -1
+		zoneName   string
+	)
+
+	// Each iteration processes one std value.
+	for {
+		var err error
+		prefix, std, suffix := nextStdChunk(layout)
+		stdstr := layout[len(prefix) : len(layout)-len(suffix)]
+		value, err = skip(value, prefix)
+		if err != nil {
+			return Time{}, &ParseError{alayout, avalue, prefix, value, ""}
+		}
+		if std == 0 {
+			if len(value) != 0 {
+				return Time{}, &ParseError{alayout, avalue, "", value, ": extra text: " + value}
+			}
+			break
+		}
+		layout = suffix
+		var p string
+		switch std & stdMask {
+		case stdYear:
+			if len(value) < 2 {
+				err = errBad
+				break
+			}
+			p, value = value[0:2], value[2:]
+			year, err = atoi(p)
+			if year >= 69 { // Unix time starts Dec 31 1969 in some time zones
+				year += 1900
+			} else {
+				year += 2000
+			}
+		case stdLongYear:
+			if len(value) < 4 || !isDigit(value, 0) {
+				err = errBad
+				break
+			}
+			p, value = value[0:4], value[4:]
+			year, err = atoi(p)
+		case stdMonth:
+			month, value, err = lookup(shortMonthNames, value)
+		case stdLongMonth:
+			month, value, err = lookup(longMonthNames, value)
+		case stdNumMonth, stdZeroMonth:
+			month, value, err = getnum(value, std == stdZeroMonth)
+			if month <= 0 || 12 < month {
+				rangeErrString = "month"
+			}
+		case stdWeekDay:
+			// Ignore weekday except for error checking.
+			_, value, err = lookup(shortDayNames, value)
+		case stdLongWeekDay:
+			_, value, err = lookup(longDayNames, value)
+		case stdDay, stdUnderDay, stdZeroDay:
+			if std == stdUnderDay && len(value) > 0 && value[0] == ' ' {
+				value = value[1:]
+			}
+			day, value, err = getnum(value, std == stdZeroDay)
+			if day < 0 || 31 < day {
+				rangeErrString = "day"
+			}
+		case stdHour:
+			hour, value, err = getnum(value, false)
+			if hour < 0 || 24 <= hour {
+				rangeErrString = "hour"
+			}
+		case stdHour12, stdZeroHour12:
+			hour, value, err = getnum(value, std == stdZeroHour12)
+			if hour < 0 || 12 < hour {
+				rangeErrString = "hour"
+			}
+		case stdMinute, stdZeroMinute:
+			min, value, err = getnum(value, std == stdZeroMinute)
+			if min < 0 || 60 <= min {
+				rangeErrString = "minute"
+			}
+		case stdSecond, stdZeroSecond:
+			sec, value, err = getnum(value, std == stdZeroSecond)
+			if sec < 0 || 60 <= sec {
+				rangeErrString = "second"
+			}
+			// Special case: do we have a fractional second but no
+			// fractional second in the format?
+			if len(value) >= 2 && value[0] == '.' && isDigit(value, 1) {
+				_, std, _ = nextStdChunk(layout)
+				std &= stdMask
+				if std == stdFracSecond0 || std == stdFracSecond9 {
+					// Fractional second in the layout; proceed normally
+					break
+				}
+				// No fractional second in the layout but we have one in the input.
+				n := 2
+				for ; n < len(value) && isDigit(value, n); n++ {
+				}
+				nsec, rangeErrString, err = parseNanoseconds(value, n)
+				value = value[n:]
+			}
+		case stdPM:
+			if len(value) < 2 {
+				err = errBad
+				break
+			}
+			p, value = value[0:2], value[2:]
+			switch p {
+			case "PM":
+				pmSet = true
+			case "AM":
+				amSet = true
+			default:
+				err = errBad
+			}
+		case stdpm:
+			if len(value) < 2 {
+				err = errBad
+				break
+			}
+			p, value = value[0:2], value[2:]
+			switch p {
+			case "pm":
+				pmSet = true
+			case "am":
+				amSet = true
+			default:
+				err = errBad
+			}
+		case stdISO8601TZ, stdISO8601ColonTZ, stdISO8601SecondsTZ, stdISO8601ColonSecondsTZ, stdNumTZ, stdNumShortTZ, stdNumColonTZ, stdNumSecondsTz, stdNumColonSecondsTZ:
+			if (std == stdISO8601TZ || std == stdISO8601ColonTZ) && len(value) >= 1 && value[0] == 'Z' {
+				value = value[1:]
+				z = UTC
+				break
+			}
+			var sign, hour, min, seconds string
+			if std == stdISO8601ColonTZ || std == stdNumColonTZ {
+				if len(value) < 6 {
+					err = errBad
+					break
+				}
+				if value[3] != ':' {
+					err = errBad
+					break
+				}
+				sign, hour, min, seconds, value = value[0:1], value[1:3], value[4:6], "00", value[6:]
+			} else if std == stdNumShortTZ {
+				if len(value) < 3 {
+					err = errBad
+					break
+				}
+				sign, hour, min, seconds, value = value[0:1], value[1:3], "00", "00", value[3:]
+			} else if std == stdISO8601ColonSecondsTZ || std == stdNumColonSecondsTZ {
+				if len(value) < 9 {
+					err = errBad
+					break
+				}
+				if value[3] != ':' || value[6] != ':' {
+					err = errBad
+					break
+				}
+				sign, hour, min, seconds, value = value[0:1], value[1:3], value[4:6], value[7:9], value[9:]
+			} else if std == stdISO8601SecondsTZ || std == stdNumSecondsTz {
+				if len(value) < 7 {
+					err = errBad
+					break
+				}
+				sign, hour, min, seconds, value = value[0:1], value[1:3], value[3:5], value[5:7], value[7:]
+			} else {
+				if len(value) < 5 {
+					err = errBad
+					break
+				}
+				sign, hour, min, seconds, value = value[0:1], value[1:3], value[3:5], "00", value[5:]
+			}
+			var hr, mm, ss int
+			hr, err = atoi(hour)
+			if err == nil {
+				mm, err = atoi(min)
+			}
+			if err == nil {
+				ss, err = atoi(seconds)
+			}
+			zoneOffset = (hr*60+mm)*60 + ss // offset is in seconds
+			switch sign[0] {
+			case '+':
+			case '-':
+				zoneOffset = -zoneOffset
+			default:
+				err = errBad
+			}
+		case stdTZ:
+			// Does it look like a time zone?
+			if len(value) >= 3 && value[0:3] == "UTC" {
+				z = UTC
+				value = value[3:]
+				break
+			}
+			n, ok := parseTimeZone(value)
+			if !ok {
+				err = errBad
+				break
+			}
+			zoneName, value = value[:n], value[n:]
+
+		case stdFracSecond0:
+			// stdFracSecond0 requires the exact number of digits as specified in
+			// the layout.
+			ndigit := 1 + (std >> stdArgShift)
+			if len(value) < ndigit {
+				err = errBad
+				break
+			}
+			nsec, rangeErrString, err = parseNanoseconds(value, ndigit)
+			value = value[ndigit:]
+
+		case stdFracSecond9:
+			if len(value) < 2 || value[0] != '.' || value[1] < '0' || '9' < value[1] {
+				// Fractional second omitted.
+				break
+			}
+			// Take any number of digits, even more than asked for,
+			// because it is what the stdSecond case would do.
+			i := 0
+			for i < 9 && i+1 < len(value) && '0' <= value[i+1] && value[i+1] <= '9' {
+				i++
+			}
+			nsec, rangeErrString, err = parseNanoseconds(value, 1+i)
+			value = value[1+i:]
+		}
+		if rangeErrString != "" {
+			return Time{}, &ParseError{alayout, avalue, stdstr, value, ": " + rangeErrString + " out of range"}
+		}
+		if err != nil {
+			return Time{}, &ParseError{alayout, avalue, stdstr, value, ""}
+		}
+	}
+	if pmSet && hour < 12 {
+		hour += 12
+	} else if amSet && hour == 12 {
+		hour = 0
+	}
+
+	if z != nil {
+		return Date(year, Month(month), day, hour, min, sec, nsec, z), nil
+	}
+
+	if zoneOffset != -1 {
+		t := Date(year, Month(month), day, hour, min, sec, nsec, UTC)
+		t.sec -= int64(zoneOffset)
+
+		// Look for local zone with the given offset.
+		// If that zone was in effect at the given time, use it.
+		name, offset, _, _, _ := local.lookup(t.sec + internalToUnix)
+		if offset == zoneOffset && (zoneName == "" || name == zoneName) {
+			t.loc = local
+			return t, nil
+		}
+
+		// Otherwise create fake zone to record offset.
+		t.loc = FixedZone(zoneName, zoneOffset)
+		return t, nil
+	}
+
+	if zoneName != "" {
+		t := Date(year, Month(month), day, hour, min, sec, nsec, UTC)
+		// Look for local zone with the given offset.
+		// If that zone was in effect at the given time, use it.
+		offset, _, ok := local.lookupName(zoneName, t.sec+internalToUnix)
+		if ok {
+			t.sec -= int64(offset)
+			t.loc = local
+			return t, nil
+		}
+
+		// Otherwise, create fake zone with unknown offset.
+		if len(zoneName) > 3 && zoneName[:3] == "GMT" {
+			offset, _ = atoi(zoneName[3:]) // Guaranteed OK by parseGMT.
+			offset *= 3600
+		}
+		t.loc = FixedZone(zoneName, offset)
+		return t, nil
+	}
+
+	// Otherwise, fall back to default.
+	return Date(year, Month(month), day, hour, min, sec, nsec, defaultLocation), nil
+}
+
+// parseTimeZone parses a time zone string and returns its length. Time zones
+// are human-generated and unpredictable. We can't do precise error checking.
+// On the other hand, for a correct parse there must be a time zone at the
+// beginning of the string, so it's almost always true that there's one
+// there. We look at the beginning of the string for a run of upper-case letters.
+// If there are more than 5, it's an error.
+// If there are 4 or 5 and the last is a T, it's a time zone.
+// If there are 3, it's a time zone.
+// Otherwise, other than special cases, it's not a time zone.
+// GMT is special because it can have an hour offset.
+func parseTimeZone(value string) (length int, ok bool) {
+	if len(value) < 3 {
+		return 0, false
+	}
+	// Special case 1: ChST and MeST are the only zones with a lower-case letter.
+	if len(value) >= 4 && (value[:4] == "ChST" || value[:4] == "MeST") {
+		return 4, true
+	}
+	// Special case 2: GMT may have an hour offset; treat it specially.
+	if value[:3] == "GMT" {
+		length = parseGMT(value)
+		return length, true
+	}
+	// How many upper-case letters are there? Need at least three, at most five.
+	var nUpper int
+	for nUpper = 0; nUpper < 6; nUpper++ {
+		if nUpper >= len(value) {
+			break
+		}
+		if c := value[nUpper]; c < 'A' || 'Z' < c {
+			break
+		}
+	}
+	switch nUpper {
+	case 0, 1, 2, 6:
+		return 0, false
+	case 5: // Must end in T to match.
+		if value[4] == 'T' {
+			return 5, true
+		}
+	case 4: // Must end in T to match.
+		if value[3] == 'T' {
+			return 4, true
+		}
+	case 3:
+		return 3, true
+	}
+	return 0, false
+}
+
+// parseGMT parses a GMT time zone. The input string is known to start "GMT".
+// The function checks whether that is followed by a sign and a number in the
+// range -14 through 12 excluding zero.
+func parseGMT(value string) int {
+	value = value[3:]
+	if len(value) == 0 {
+		return 3
+	}
+	sign := value[0]
+	if sign != '-' && sign != '+' {
+		return 3
+	}
+	x, rem, err := leadingInt(value[1:])
+	if err != nil {
+		return 3
+	}
+	if sign == '-' {
+		x = -x
+	}
+	if x == 0 || x < -14 || 12 < x {
+		return 3
+	}
+	return 3 + len(value) - len(rem)
+}
+
+func parseNanoseconds(value string, nbytes int) (ns int, rangeErrString string, err error) {
+	if value[0] != '.' {
+		err = errBad
+		return
+	}
+	if ns, err = atoi(value[1:nbytes]); err != nil {
+		return
+	}
+	if ns < 0 || 1e9 <= ns {
+		rangeErrString = "fractional second"
+		return
+	}
+	// We need nanoseconds, which means scaling by the number
+	// of missing digits in the format, maximum length 10. If it's
+	// longer than 10, we won't scale.
+	scaleDigits := 10 - nbytes
+	for i := 0; i < scaleDigits; i++ {
+		ns *= 10
+	}
+	return
+}
+
+var errLeadingInt = errors.New("time: bad [0-9]*") // never printed
+
+// leadingInt consumes the leading [0-9]* from s.
+func leadingInt(s string) (x int64, rem string, err error) {
+	i := 0
+	for ; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			break
+		}
+		if x >= (1<<63-10)/10 {
+			// overflow
+			return 0, "", errLeadingInt
+		}
+		x = x*10 + int64(c) - '0'
+	}
+	return x, s[i:], nil
+}
+
+var unitMap = map[string]float64{
+	"ns": float64(Nanosecond),
+	"us": float64(Microsecond),
+	"µs": float64(Microsecond), // U+00B5 = micro symbol
+	"μs": float64(Microsecond), // U+03BC = Greek letter mu
+	"ms": float64(Millisecond),
+	"s":  float64(Second),
+	"m":  float64(Minute),
+	"h":  float64(Hour),
+}
+
+// ParseDuration parses a duration string.
+// A duration string is a possibly signed sequence of
+// decimal numbers, each with optional fraction and a unit suffix,
+// such as "300ms", "-1.5h" or "2h45m".
+// Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
+func ParseDuration(s string) (Duration, error) {
+	// [-+]?([0-9]*(\.[0-9]*)?[a-z]+)+
+	orig := s
+	f := float64(0)
+	neg := false
+
+	// Consume [-+]?
+	if s != "" {
+		c := s[0]
+		if c == '-' || c == '+' {
+			neg = c == '-'
+			s = s[1:]
+		}
+	}
+	// Special case: if all that is left is "0", this is zero.
+	if s == "0" {
+		return 0, nil
+	}
+	if s == "" {
+		return 0, errors.New("time: invalid duration " + orig)
+	}
+	for s != "" {
+		g := float64(0) // this element of the sequence
+
+		var x int64
+		var err error
+
+		// The next character must be [0-9.]
+		if !(s[0] == '.' || ('0' <= s[0] && s[0] <= '9')) {
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+		// Consume [0-9]*
+		pl := len(s)
+		x, s, err = leadingInt(s)
+		if err != nil {
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+		g = float64(x)
+		pre := pl != len(s) // whether we consumed anything before a period
+
+		// Consume (\.[0-9]*)?
+		post := false
+		if s != "" && s[0] == '.' {
+			s = s[1:]
+			pl := len(s)
+			x, s, err = leadingInt(s)
+			if err != nil {
+				return 0, errors.New("time: invalid duration " + orig)
+			}
+			scale := 1.0
+			for n := pl - len(s); n > 0; n-- {
+				scale *= 10
+			}
+			g += float64(x) / scale
+			post = pl != len(s)
+		}
+		if !pre && !post {
+			// no digits (e.g. ".s" or "-.s")
+			return 0, errors.New("time: invalid duration " + orig)
+		}
+
+		// Consume unit.
+		i := 0
+		for ; i < len(s); i++ {
+			c := s[i]
+			if c == '.' || ('0' <= c && c <= '9') {
+				break
+			}
+		}
+		if i == 0 {
+			return 0, errors.New("time: missing unit in duration " + orig)
+		}
+		u := s[:i]
+		s = s[i:]
+		unit, ok := unitMap[u]
+		if !ok {
+			return 0, errors.New("time: unknown unit " + u + " in duration " + orig)
+		}
+
+		f += g * unit
+	}
+
+	if neg {
+		f = -f
+	}
+	if f < float64(-1<<63) || f > float64(1<<63-1) {
+		return 0, errors.New("time: overflow parsing duration")
+	}
+	return Duration(f), nil
+}