dateparse/parseany.go

package dateparse

import (
	"fmt"
	"strconv"
	"time"
	"unicode"
	"unicode/utf8"
)

type DateState int

const (
	ST_START DateState = iota
	ST_DIGIT
	ST_DIGITDASH
	ST_DIGITDASHWS
	ST_DIGITDASHWSALPHA
	ST_DIGITDASHWSDOT
	ST_DIGITDASHWSDOTALPHA
	ST_DIGITDASHWSDOTPLUS
	ST_DIGITDASHWSDOTPLUSALPHA
	ST_DIGITDASHT
	ST_DIGITDASHTZ
	ST_DIGITDASHTZDIGIT
	ST_DIGITDASHTDASH
	ST_DIGITCOMMA
	ST_DIGITCOLON
	ST_DIGITSLASH
	ST_DIGITSLASHWS
	ST_DIGITSLASHWSCOLON
	ST_DIGITSLASHWSCOLONAMPM
	ST_DIGITSLASHWSCOLONCOLON
	ST_DIGITSLASHWSCOLONCOLONAMPM
	ST_DIGITALPHA
	ST_ALPHA
	ST_ALPHAWS
	ST_ALPHAWSCOMMA
	ST_ALPHAWSALPHA
	ST_ALPHACOMMA
	ST_ALPHACOMMADASH
	ST_ALPHACOMMADASHDASH
	ST_MONTHCOMMA
	ST_WEEKDAYCOMMA
	ST_WEEKDAYABBREVCOMMA
)

var (
	shortDates    = []string{"01/02/2006", "1/2/2006", "06/01/02", "01/02/06", "1/2/06"}
	weekdays      = map[string]bool{"Monday": true, "Tuesday": true, "Wednesday": true, "Thursday": true, "Friday": true, "Saturday": true, "Sunday": true}
	weekdayAbbrev = map[string]bool{"Mon": true, "Tue": true, "Wed": true, "Thu": true, "Fri": true, "Sat": true, "Sun": true}
)

// Parse a date, and panic if it can't be parsed
func MustParse(datestr string) time.Time {
	t, err := ParseAny(datestr)
	if err != nil {
		panic(err.Error())
	}
	return t
}

// Given an unknown date format, detect the type, parse, return time
func ParseAny(datestr string) (time.Time, error) {

	state := ST_START

	firstSlash := 0

	// General strategy is to read rune by rune through the date looking for
	// certain hints of what type of date we are dealing with.
	// Hopefully we only need to read about 5 or 6 bytes before
	// we figure it out and then attempt a parse
iterRunes:
	for i := 0; i < len(datestr); i++ {
		r, bytesConsumed := utf8.DecodeRuneInString(datestr[i:])
		if bytesConsumed > 1 {
			i += (bytesConsumed - 1)
		}

		switch state {
		case ST_START:
			if unicode.IsDigit(r) {
				state = ST_DIGIT
			} else if unicode.IsLetter(r) {
				state = ST_ALPHA
			}
		case ST_DIGIT: // starts digits
			if unicode.IsDigit(r) {
				continue
			} else if unicode.IsLetter(r) {
				state = ST_DIGITALPHA
				continue
			}
			switch r {
			case ',':
				state = ST_DIGITCOMMA
			case '-':
				state = ST_DIGITDASH
			case ':':
				state = ST_DIGITCOLON
			case '/':
				state = ST_DIGITSLASH
				firstSlash = i
			}
		case ST_DIGITDASH: // starts digit then dash 02-
			// 2006-01-02T15:04:05Z07:00
			// 2017-06-25T17:46:57.45706582-07:00
			// 2006-01-02T15:04:05.999999999Z07:00
			// 2012-08-03 18:31:59.257000000
			// 2014-04-26 17:24:37.3186369
			// 2017-01-27 00:07:31.945167
			// 2016-03-14 00:00:00.000
			// 2014-05-11 08:20:13,787
			// 2006-01-02
			// 2013-04-01 22:43:22
			// 2014-04-26 05:24:37 PM
			switch {
			case r == ' ':
				state = ST_DIGITDASHWS
			case r == 'T':
				state = ST_DIGITDASHT
			}
		case ST_DIGITDASHWS: // starts digit then dash 02- then whitespace
			// 2013-04-01 22:43:22
			// 2014-05-11 08:20:13,787
			// 2014-04-26 05:24:37 PM
			// 2014-12-16 06:20:00 UTC
			// 2015-02-18 00:12:00 +0000 UTC
			// 2015-06-25 01:25:37.115208593 +0000 UTC
			switch r {
			case 'A', 'P':
				if len(datestr) == len("2014-04-26 03:24:37 PM") {
					if t, err := time.Parse("2006-01-02 03:04:05 PM", datestr); err == nil {
						return t, nil
					} else {
						return time.Time{}, err
					}
				}
			case ',':
				if len(datestr) == len("2014-05-11 08:20:13,787") {
					// go doesn't seem to parse this one natively?   or did i miss it?
					if t, err := time.Parse("2006-01-02 03:04:05", datestr[:i]); err == nil {
						ms, err := strconv.Atoi(datestr[i+1:])
						if err == nil {
							return time.Unix(0, t.UnixNano()+int64(ms)*1e6), nil
						}
						return time.Time{}, err
					} else {
						return time.Time{}, err
					}
				}
			case '.':
				state = ST_DIGITDASHWSDOT
			default:
				if unicode.IsLetter(r) {
					// 2014-12-16 06:20:00 UTC
					state = ST_DIGITDASHWSALPHA
					break iterRunes
				}
			}
		case ST_DIGITDASHWSDOT:
			// 2014-04-26 17:24:37.3186369
			// 2017-01-27 00:07:31.945167
			// 2012-08-03 18:31:59.257000000
			// 2016-03-14 00:00:00.000
			if unicode.IsLetter(r) {
				// 2014-12-16 06:20:00.000 UTC
				state = ST_DIGITDASHWSDOTALPHA
				break iterRunes
			} else if r == '+' || r == '-' {
				state = ST_DIGITDASHWSDOTPLUS
			}
		case ST_DIGITDASHWSDOTPLUS:
			// 2014-04-26 17:24:37.3186369
			// 2017-01-27 00:07:31.945167
			// 2012-08-03 18:31:59.257000000
			// 2016-03-14 00:00:00.000
			if unicode.IsLetter(r) {
				// 2014-12-16 06:20:00.000 UTC
				state = ST_DIGITDASHWSDOTPLUSALPHA
				break iterRunes
			}

		case ST_DIGITDASHT: // starts digit then dash 02-  then T
			// ST_DIGITDASHT
			// 2006-01-02T15:04:05
			// ST_DIGITDASHTZ
			// 2006-01-02T15:04:05.999999999Z
			// 2006-01-02T15:04:05.99999999Z
			// 2006-01-02T15:04:05.9999999Z
			// 2006-01-02T15:04:05.999999Z
			// 2006-01-02T15:04:05.99999Z
			// 2006-01-02T15:04:05.9999Z
			// 2006-01-02T15:04:05.999Z
			// 2006-01-02T15:04:05.99Z
			// ST_DIGITDASHTZDIGIT
			// 2006-01-02T15:04:05.999999999Z07:00
			// 2006-01-02T15:04:05Z07:00
			// With another dash aka time-zone at end
			// ST_DIGITDASHTDASH
			// 2017-06-25T17:46:57.45706582-07:00
			switch {
			case r == '-':
				state = ST_DIGITDASHTDASH
			case r == 'Z':
				state = ST_DIGITDASHTZ
			}
		case ST_DIGITDASHTZ:
			if unicode.IsDigit(r) {
				state = ST_DIGITDASHTZDIGIT
			}
		case ST_DIGITSLASH: // starts digit then slash 02/
			// 2014/07/10 06:55:38.156283
			// 03/19/2012 10:11:59
			// 04/2/2014 03:00:37
			// 3/1/2012 10:11:59
			// 4/8/2014 22:05
			// 3/1/2014
			// 10/13/2014
			// 01/02/2006
			// 1/2/06
			if unicode.IsDigit(r) || r == '/' {
				continue
			}
			switch r {
			case ' ':
				state = ST_DIGITSLASHWS
			}
		case ST_DIGITSLASHWS: // starts digit then slash 02/ more digits/slashes then whitespace
			// 2014/07/10 06:55:38.156283
			// 03/19/2012 10:11:59
			// 04/2/2014 03:00:37
			// 3/1/2012 10:11:59
			// 4/8/2014 22:05
			switch r {
			case ':':
				state = ST_DIGITSLASHWSCOLON
			}
		case ST_DIGITSLASHWSCOLON: // starts digit then slash 02/ more digits/slashes then whitespace
			// 2014/07/10 06:55:38.156283
			// 03/19/2012 10:11:59
			// 04/2/2014 03:00:37
			// 3/1/2012 10:11:59
			// 4/8/2014 22:05
			// 3/1/2012 10:11:59 AM
			switch r {
			case ':':
				state = ST_DIGITSLASHWSCOLONCOLON
			case 'A', 'P':
				state = ST_DIGITSLASHWSCOLONAMPM
			}
		case ST_DIGITSLASHWSCOLONCOLON: // starts digit then slash 02/ more digits/slashes then whitespace
			// 2014/07/10 06:55:38.156283
			// 03/19/2012 10:11:59
			// 04/2/2014 03:00:37
			// 3/1/2012 10:11:59
			// 4/8/2014 22:05
			// 3/1/2012 10:11:59 AM
			switch r {
			case 'A', 'P':
				state = ST_DIGITSLASHWSCOLONCOLONAMPM
			}
		case ST_DIGITALPHA:
			// 12 Feb 2006, 19:17
			// 12 Feb 2006, 19:17:22
			switch {
			case len(datestr) == len("02 Jan 2006, 15:04"):
				if t, err := time.Parse("02 Jan 2006, 15:04", datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			case len(datestr) == len("02 Jan 2006, 15:04:05"):
				if t, err := time.Parse("02 Jan 2006, 15:04:05", datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			default:
			}
		case ST_ALPHA: // starts alpha
			// May 8, 2009 5:57:51 PM
			// Mon Jan _2 15:04:05 2006
			// Mon Jan _2 15:04:05 MST 2006
			// Mon Jan 02 15:04:05 -0700 2006
			// Monday, 02-Jan-06 15:04:05 MST
			// Monday, 02 Jan 2006 15:04:05 -0700
			// Mon, 02 Jan 2006 15:04:05 MST
			// Mon, 02 Jan 2006 15:04:05 -0700
			// Mon Aug 10 15:44:11 UTC+0100 2015
			// Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)
			if unicode.IsLetter(r) {
				continue
			}
			switch {
			case r == ' ':
				state = ST_ALPHAWS
			case r == ',':

				switch {
				case weekdays[datestr[:i]] == true:
					state = ST_WEEKDAYCOMMA
				case weekdayAbbrev[datestr[:i]] == true:
					state = ST_WEEKDAYABBREVCOMMA
				default:
					state = ST_MONTHCOMMA
				}
			}
		case ST_WEEKDAYCOMMA: // Starts alpha then comma
			// Monday, 02-Jan-06 15:04:05 MST
			// Monday, 02 Jan 2006 15:04:05 -0700
			switch {
			case r == '-':
				if i < 15 {
					t, err := time.Parse("Monday, 02-Jan-06 15:04:05 MST", datestr)
					if err == nil {
						return t, nil
					}
					return time.Time{}, err
				} else {
					t, err := time.Parse("Monday, 02 Jan 2006 15:04:05 -0700", datestr)
					if err == nil {
						return t, nil
					}
					return time.Time{}, err
				}
			}
		case ST_WEEKDAYABBREVCOMMA: // Starts alpha then comma
			// Mon, 02-Jan-06 15:04:05 MST
			// Mon, 02 Jan 2006 15:04:05 -0700
			switch {
			case r == '-':
				if i < 15 {
					t, err := time.Parse("Mon, 02-Jan-06 15:04:05 MST", datestr)
					if err == nil {
						return t, nil
					}
					return time.Time{}, err
				} else {
					t, err := time.Parse("Mon, 02 Jan 2006 15:04:05 -0700", datestr)
					if err == nil {
						return t, nil
					}
					return time.Time{}, err
				}
			}

		case ST_ALPHAWS: // Starts alpha then whitespace
			// May 8, 2009 5:57:51 PM
			// Mon Jan _2 15:04:05 2006
			// Mon Jan _2 15:04:05 MST 2006
			// Mon Jan 02 15:04:05 -0700 2006
			// Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)
			// Mon Aug 10 15:44:11 UTC+0100 2015
			switch {
			// case r == ' ':
			// 	state = ST_ALPHAWSWS
			case r == ',':
				state = ST_ALPHAWSCOMMA
			case unicode.IsLetter(r):
				state = ST_ALPHAWSALPHA
			}
		case ST_ALPHACOMMA: // Starts alpha then comma
			// Mon, 02 Jan 2006 15:04:05 MST
			// Mon, 02 Jan 2006 15:04:05 -0700
			switch {
			case r == '-':
				state = ST_ALPHACOMMADASH
			}
		case ST_ALPHACOMMADASH: // Starts alpha then comma and one dash
			// Mon, 02 Jan 2006 15:04:05 -0700
			switch {
			case r == '-':
				state = ST_ALPHACOMMADASHDASH
			}

		case ST_ALPHAWSCOMMA: // Starts Alpha, whitespace, digit, comma
			// May 8, 2009 5:57:51 PM
			t, err := time.Parse("Jan 2, 2006 3:04:05 PM", datestr)
			if err == nil {
				return t, nil
			}
			return time.Time{}, err
		case ST_ALPHAWSALPHA: // Starts Alpha, whitespace, alpha
			// Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)
			// Mon Jan _2 15:04:05 2006
			// Mon Jan _2 15:04:05 MST 2006
			// Mon Jan 02 15:04:05 -0700 2006
			// Mon Aug 10 15:44:11 UTC+0100 2015
			switch {
			case len(datestr) == len("Mon Jan _2 15:04:05 2006"):
				if t, err := time.Parse(time.ANSIC, datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			case len(datestr) == len("Mon Jan _2 15:04:05 MST 2006"):
				if t, err := time.Parse(time.UnixDate, datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			case len(datestr) == len("Mon Jan 02 15:04:05 -0700 2006"):
				if t, err := time.Parse(time.RubyDate, datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			case len(datestr) == len("Mon Aug 10 15:44:11 UTC+0100 2015"):
				if t, err := time.Parse("Mon Jan 02 15:04:05 MST-0700 2006", datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			case len(datestr) > len("Mon Jan 02 2006 15:04:05 MST-0700"):
				// What effing time stamp is this?
				// Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)
				dateTmp := datestr[:33]
				if t, err := time.Parse("Mon Jan 02 2006 15:04:05 MST-0700", dateTmp); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			default:
			}
		default:
			break iterRunes
		}
	}

	/*
		ST_DIGITDASHT
		ST_DIGITDASHTZ
		ST_DIGITDASHTZDIGIT
		ST_DIGITDASHTDASH

		// ST_DIGITDASHT
		// 2006-01-02T15:04:05
		// ST_DIGITDASHTZ
		// 2006-01-02T15:04:05.999999999Z
		// 2006-01-02T15:04:05.99999999Z
		// 2006-01-02T15:04:05.9999999Z
		// 2006-01-02T15:04:05.999999Z
		// 2006-01-02T15:04:05.99999Z
		// 2006-01-02T15:04:05.9999Z
		// 2006-01-02T15:04:05.999Z
		// 2006-01-02T15:04:05.99Z
		// ST_DIGITDASHTZDIGIT
		// 2006-01-02T15:04:05.999999999Z07:00
		// 2006-01-02T15:04:05Z07:00
		// With another dash aka time-zone at end
		// ST_DIGITDASHTDASH
		// 2017-06-25T17:46:57.45706582-07:00
	*/
	switch state {
	case ST_DIGIT:
		// unixy timestamps ish
		//  13980450781991351    nanoseconds
		//  13980450781991       microseconds
		//  1384216367189
		//  1332151919           seconds
		//  20140601             yyyymmdd
		//  2014                 yyyy
		if len(datestr) >= len("13980450781991351") {
			if nanoSecs, err := strconv.ParseInt(datestr, 10, 64); err == nil {
				return time.Unix(0, nanoSecs), nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) >= len("13980450781991") {
			if microSecs, err := strconv.ParseInt(datestr, 10, 64); err == nil {
				return time.Unix(0, microSecs*1000), nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) >= len("1384216367189") {
			if miliSecs, err := strconv.ParseInt(datestr, 10, 64); err == nil {
				return time.Unix(0, miliSecs*1000*1000), nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("20140601") {
			if t, err := time.Parse("20060102", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2014") {
			if t, err := time.Parse("2006", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else {
			if secs, err := strconv.ParseInt(datestr, 10, 64); err == nil {
				return time.Unix(secs, 0), nil
			} else {
				return time.Time{}, err
			}
		}
	case ST_DIGITDASH: // starts digit then dash 02-
		// 2006-01-02
		// 2006-01
		if len(datestr) == len("2014-04-26") {
			if t, err := time.Parse("2006-01-02", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2014-04") {
			if t, err := time.Parse("2006-01", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		}
	case ST_DIGITDASHTDASH:
		// With another dash aka time-zone at end
		// 2006-01-02T15:04:05.999999999-07:00
		// 2006-01-02T15:04:05.99999999-07:00
		// 2006-01-02T15:04:05.9999999-07:00
		// 2006-01-02T15:04:05.999999-07:00
		// 2006-01-02T15:04:05.99999-07:00
		// 2006-01-02T15:04:05.9999-07:00
		// 2006-01-02T15:04:05.999-07:00
		// 2006-01-02T15:04:05.99-07:00
		if len(datestr) == len("2006-01-02T15:04:05.999999999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.999999999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.99999999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.99999999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.9999999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.9999999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.999999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.999999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.99999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.99999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.9999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.9999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.999-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.999-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.99-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.99-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05.9-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05.9-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		} else if len(datestr) == len("2006-01-02T15:04:05-07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05-07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		}
	case ST_DIGITDASHTZDIGIT:
		// With a time-zone at end after Z
		// 2006-01-02T15:04:05.999999999Z07:00
		// 2006-01-02T15:04:05Z07:00
		if len(datestr) == len("2006-01-02T15:04:05Z07:00") {
			if t, err := time.Parse("2006-01-02T15:04:05Z07:00", datestr); err == nil {
				return t, nil
			} else {
				return time.Time{}, err
			}
		}
	case ST_DIGITDASHT: // starts digit then dash 02-  then T
		// 2006-01-02T15:04:05.999999
		// 2006-01-02T15:04:05.999999
		if t, err := time.Parse("2006-01-02T15:04:05", datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}
	case ST_DIGITDASHTZ: // starts digit then dash 02-  then T Then Z
		// 2006-01-02T15:04:05.999999999Z
		// 2006-01-02T15:04:05.99999999Z
		// 2006-01-02T15:04:05.9999999Z
		// 2006-01-02T15:04:05.999999Z
		// 2006-01-02T15:04:05.99999Z
		// 2006-01-02T15:04:05.9999Z
		// 2006-01-02T15:04:05.999Z
		// 2006-01-02T15:04:05.99Z
		if t, err := time.Parse("2006-01-02T15:04:05Z", datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}
	case ST_DIGITDASHWS: // starts digit then dash 02-  then whitespace   1 << 2  << 5 + 3
		// 2013-04-01 22:43:22
		var t time.Time
		var err error

		switch len(datestr) {
		case len("2006-01-02 15:04:05"):
			t, err = time.Parse("2006-01-02 15:04:05", datestr)
		case len("2006-01-02 15:04:05 -0700"):
			t, err = time.Parse("2006-01-02 15:04:05 -0700", datestr)
		case len("2006-01-02 15:04:05 -07:00"):
			t, err = time.Parse("2006-01-02 15:04:05 -07:00", datestr)
		}
		return t, err
	case ST_DIGITDASHWSALPHA: // starts digit then dash 02-  then whitespace   1 << 2  << 5 + 3
		// 2014-12-16 06:20:00 UTC
		// 2015-02-18 00:12:00 +0000 UTC
		// 2015-06-25 01:25:37.115208593 +0000 UTC
		var t time.Time
		var err error

		switch len(datestr) {
		case len("2006-01-02 15:04:05 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05 GMT", datestr)
			}
		case len("2015-02-18 00:12:00 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05 -0700 GMT", datestr)
			}
		}
		if err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_DIGITDASHWSDOT:
		// 2012-08-03 18:31:59.257000000
		// 2014-04-26 17:24:37.3186369
		// 2017-01-27 00:07:31.945167
		// 2016-03-14 00:00:00.000
		if t, err := time.Parse("2006-01-02 15:04:05", datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_DIGITDASHWSDOTALPHA:
		// 2012-08-03 18:31:59.257000000 UTC
		// 2014-04-26 17:24:37.3186369 UTC
		// 2017-01-27 00:07:31.945167 UTC
		// 2016-03-14 00:00:00.000 UTC
		var t time.Time
		var err error

		switch len(datestr) {
		case len("2012-08-03 18:31:59.123456789 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.000000000 UTC", datestr)
		case len("2014-04-26 05:24:37.12345678 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00000000 UTC", datestr)
		case len("2014-04-26 05:24:37.1234567 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0000000 UTC", datestr)
		case len("2014-04-26 05:24:37.123456 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.000000 UTC", datestr)
		case len("2014-04-26 05:24:37.12345 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00000 UTC", datestr)
		case len("2014-04-26 05:24:37.1234 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0000 UTC", datestr)
		case len("2014-04-26 05:24:37.000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.000 UTC", datestr)
		case len("2014-04-26 05:24:37.00 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00 UTC", datestr)
		case len("2014-04-26 05:24:37.0 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0 UTC", datestr)
		}
		if err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_DIGITDASHWSDOTPLUS:
		// 2012-08-03 18:31:59.257000000 +0000
		// 2014-04-26 17:24:37.3186369 +0000
		// 2017-01-27 00:07:31.945167 +0000
		// 2016-03-14 00:00:00.000 +0000
		var t time.Time
		var err error

		switch len(datestr) {
		case len("2012-08-03 18:31:59.123456789 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.000000000 -0700", datestr)
		case len("2014-04-26 05:24:37.12345678 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.00000000 -0700", datestr)
		case len("2014-04-26 05:24:37.1234567 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.0000000 -0700", datestr)
		case len("2014-04-26 05:24:37.123456 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.000000 -0700", datestr)
		case len("2014-04-26 05:24:37.12345 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.00000 -0700", datestr)
		case len("2014-04-26 05:24:37.1234 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.0000 -0700", datestr)
		case len("2014-04-26 05:24:37.000 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.000 -0700", datestr)
		case len("2014-04-26 05:24:37.00 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.00 -0700", datestr)
		case len("2014-04-26 05:24:37.0 +0000"):
			t, err = time.Parse("2006-01-02 15:04:05.0 -0700", datestr)
		}
		if err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_DIGITDASHWSDOTPLUSALPHA:
		// 2012-08-03 18:31:59.257000000 +0000 UTC
		// 2014-04-26 17:24:37.3186369 +0000 UTC
		// 2017-01-27 00:07:31.945167 +0000 UTC
		// 2016-03-14 00:00:00.000 +0000 UTC
		var t time.Time
		var err error

		switch len(datestr) {
		case len("2015-06-25 01:25:37.123456789 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.000000000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.000000000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.12345678 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00000000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.00000000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.1234567 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0000000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.0000000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.123456 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.000000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.000000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.12345 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.00000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.1234 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.0000 -0700 GMT", datestr)
			}
			t, err = time.Parse("2006-01-02 15:04:05.000 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.000 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.12 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.00 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.00 -0700 GMT", datestr)
			}
		case len("2015-09-30 18:48:56.1 +0000 UTC"):
			t, err = time.Parse("2006-01-02 15:04:05.0 -0700 UTC", datestr)
			if err != nil {
				t, err = time.Parse("2006-01-02 15:04:05.0 -0700 GMT", datestr)
			}
		}
		if err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_DIGITSLASH: // starts digit then slash 02/ (but nothing else)
		// 3/1/2014
		// 10/13/2014
		// 01/02/2006
		// 2014/10/13
		if firstSlash == 4 {
			if len(datestr) == len("2006/01/02") {
				if t, err := time.Parse("2006/01/02", datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			} else {
				if t, err := time.Parse("2006/1/2", datestr); err == nil {
					return t, nil
				} else {
					return time.Time{}, err
				}
			}
		} else {
			for _, parseFormat := range shortDates {
				if t, err := time.Parse(parseFormat, datestr); err == nil {
					return t, nil
				}
			}

			return time.Time{}, fmt.Errorf("Unrecognized dateformat: %v", datestr)
		}

	case ST_DIGITSLASHWSCOLON: // starts digit then slash 02/ more digits/slashes then whitespace
		// 4/8/2014 22:05
		// 04/08/2014 22:05
		// 2014/4/8 22:05
		// 2014/04/08 22:05

		var t time.Time
		var err error

		if firstSlash == 4 {
			switch len(datestr) {
			case len("2006/01/02 15:04"):
				t, err = time.Parse("2006/01/02 15:04", datestr)
			case len("2006/01/2 15:04"):
				if t, err = time.Parse("2006/01/2 15:04", datestr); err != nil {
					t, err = time.Parse("2006/1/02 15:04", datestr)
				} else if t, err = time.Parse("2006/1/02 15:04", datestr); err != nil {
					t, err = time.Parse("2006/1/02 15:04", datestr)
				}
			default:
				t, err = time.Parse("2006/1/2 15:04", datestr)
			}
		} else {
			switch len(datestr) {
			case len("01/02/2006 15:04"):
				t, err = time.Parse("01/02/2006 15:04", datestr)
			case len("01/2/2006 15:04"):
				if t, err = time.Parse("01/2/2006 15:04", datestr); err != nil {
					t, err = time.Parse("1/02/2006 15:04", datestr)
				} else if t, err = time.Parse("1/02/2006 15:04", datestr); err != nil {
					t, err = time.Parse("1/02/2006 15:04", datestr)
				}
			default:
				t, err = time.Parse("1/2/2006 15:04", datestr)
			}
		}
		if err == nil {
			return t, nil
		}
		return time.Time{}, err

	case ST_DIGITSLASHWSCOLONAMPM: // starts digit then slash 02/ more digits/slashes then whitespace
		// 4/8/2014 22:05 PM
		// 04/08/2014 22:05 PM
		// 2014/4/8 22:05 PM
		// 2014/04/08 22:05 PM

		var t time.Time
		var err error

		if firstSlash == 4 {
			switch len(datestr) {
			case len("2006/01/02 15:04 PM"):
				t, err = time.Parse("2006/01/02 03:04 PM", datestr)
			case len("2006/01/2 15:04 PM"):
				if t, err = time.Parse("2006/01/2 03:04 PM", datestr); err != nil {
					t, err = time.Parse("2006/1/02 03:04 PM", datestr)
				}
			default:
				t, err = time.Parse("2006/1/2 03:04 PM", datestr)
			}
		} else {
			switch len(datestr) {
			case len("01/02/2006 15:04 PM"):
				t, err = time.Parse("01/02/2006 03:04 PM", datestr)
			case len("01/2/2006 15:04 PM"):
				if t, err = time.Parse("01/2/2006 03:04 PM", datestr); err != nil {
					t, err = time.Parse("1/02/2006 03:04 PM", datestr)
				}
			default:
				t, err = time.Parse("1/2/2006 3:04 PM", datestr)
			}
		}
		if err == nil {
			return t, nil
		}
		return time.Time{}, err

	case ST_DIGITSLASHWSCOLONCOLON: // starts digit then slash 02/ more digits/slashes then whitespace double colons
		// 2014/07/10 06:55:38.156283
		// 03/19/2012 10:11:59
		// 3/1/2012 10:11:59
		// 03/1/2012 10:11:59
		// 3/01/2012 10:11:59

		var t time.Time
		var err error

		if firstSlash == 4 {
			switch len(datestr) {
			case len("2014/07/10 06:55:38.156283"):
				t, err = time.Parse("2006/01/02 15:04:05.000000", datestr)
			case len("2006/01/02 15:04:05"):
				t, err = time.Parse("2006/01/02 15:04:05", datestr)
			case len("2006/01/2 15:04:05"):
				if t, err = time.Parse("2006/01/2 15:04:05", datestr); err != nil {
					t, err = time.Parse("2006/1/02 15:04:05", datestr)
				}
			default:
				t, err = time.Parse("2006/1/2 15:04:05", datestr)
			}
		} else {
			switch len(datestr) {
			case len("07/10/2014 06:55:38.156283"):
				t, err = time.Parse("01/02/2006 15:04:05.000000", datestr)
			case len("01/02/2006 15:04:05"):
				t, err = time.Parse("01/02/2006 15:04:05", datestr)
			case len("01/2/2006 15:04:05"):
				if t, err = time.Parse("01/2/2006 15:04:05", datestr); err != nil {
					t, err = time.Parse("1/02/2006 15:04:05", datestr)
				}
			default:
				t, err = time.Parse("1/2/2006 15:04:05", datestr)
			}
		}
		if err == nil {
			return t, nil
		}
		return time.Time{}, err

	case ST_DIGITSLASHWSCOLONCOLONAMPM: // starts digit then slash 02/ more digits/slashes then whitespace double colons
		// 2014/07/10 06:55:38.156283 PM
		// 03/19/2012 10:11:59 PM
		// 3/1/2012 10:11:59 PM
		// 03/1/2012 10:11:59 PM
		// 3/01/2012 10:11:59 PM

		var t time.Time
		var err error

		if firstSlash == 4 {
			switch len(datestr) {
			case len("2014/07/10 06:55:38.156283 PM"):
				t, err = time.Parse("2006/01/02 03:04:05.000000 PM", datestr)
			case len("2006/01/02 15:04:05 PM"):
				t, err = time.Parse("2006/01/02 03:04:05 PM", datestr)
			case len("2006/01/2 15:04:05 PM"):
				if t, err = time.Parse("2006/01/2 03:04:05 PM", datestr); err != nil {
					t, err = time.Parse("2006/1/02 03:04:05 PM", datestr)
				}
			default:
				t, err = time.Parse("2006/1/2 03:04:05 PM", datestr)
			}
		} else {
			switch len(datestr) {
			case len("07/10/2014 06:55:38.156283 PM"):
				t, err = time.Parse("01/02/2006 03:04:05.000000 PM", datestr)
			case len("01/02/2006 15:04:05 PM"):
				t, err = time.Parse("01/02/2006 03:04:05 PM", datestr)
			case len("01/2/2006 15:04:05 PM"):
				if t, err = time.Parse("01/2/2006 03:04:05 PM", datestr); err != nil {
					t, err = time.Parse("1/02/2006 03:04:05 PM", datestr)
				}
			default:
				t, err = time.Parse("1/2/2006 03:04:05 PM", datestr)
			}
		}
		if err == nil {
			return t, nil
		}
		return time.Time{}, err

	case ST_WEEKDAYABBREVCOMMA: // Starts alpha then comma
		// Mon, 02 Jan 2006 15:04:05 MST
		t, err := time.Parse("Mon, 02 Jan 2006 15:04:05 MST", datestr)
		if err == nil {
			return t, nil
		}
		return time.Time{}, err

	case ST_ALPHACOMMA: // Starts alpha then comma but no DASH
		// Mon, 02 Jan 2006 15:04:05 MST
		// Jan 2, 2006 3:04:05 PM
		if t, err := time.Parse("Jan 2, 2006 3:04:05 PM", datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}
	case ST_ALPHACOMMADASH: // Starts alpha then comma and one dash
		// Mon, 02 Jan 2006 15:04:05 -0700

		//RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone
		// TODO:  this doesn't work???
		if t, err := time.Parse(time.RFC1123Z, datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}

	case ST_ALPHACOMMADASHDASH: // Starts alpha then comma and two dash'es
		// Monday, 02-Jan-06 15:04:05 MST
		if t, err := time.Parse("Monday, 02-Jan-06 15:04:05 MST", datestr); err == nil {
			return t, nil
		} else {
			return time.Time{}, err
		}
	}

	return time.Time{}, fmt.Errorf("Could not find date format for %s", datestr)
}