https://github.com/olooney/attache-date-js

License And History
-------------------

This is a fork of Baron Schwartz's date formatting and parsing library.  I
added namespacing, simplified the function generators, wrote unit tests, and
fixed some bugs. It no longer installs anything onto Date's prototype.  It
remains under the LPGL. I would like to stress that all the core design ideas
(namely the code generator approach) and legwork of implementing the many
different formatting flags are his; I'm simply doing some clean-up to ensure
that the libary is up to recent JS library standards.

Baron's original README follow:
This is a JavaScript date parsing and formatting library, date-functions.js.

Copyright (C) 2006 Baron Schwartz <baron at sequent dot org>
Copyright (C) 2011 Oran Looney <olooney at gmail dot com>

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free
Software Foundation, version 2.1.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
details.

Changelog:

2006-07-08 Revision 1.1
2011-11-24 Revision 2.0


Documentation
-------------

attache.date.format: function(Date d, String format) -> String
  Formats the given Date object according to the PHP
  date format string. If d is not a Date, returns "".

attache.date.parse: function(String input, String format) -> Date
  Accepts a string and a PHP date mask and returns a Date
  object if the input string can be interpretted as a Date 
  according to the mask format.

attache.date.monthNames: string[]
  "January" through "December".

attache.date.dayNames: string[]
  "Sunday" through "Saturday".

attache.date.y2kYear: Number
  This is the cutoff point for 1900 vs 2000.  by default it is 50, so that
  2-digit years are between 1950 and 2049. You may change it if you like.
  For example, you'd set y2kYear = 30 to emulate Excel's "2029 rule."

attache.date.monthNumbers: Object
  Reverse lookup table of 3-letter month abbreviations to index. 
  For example, attache.date.monthNumbers['Feb'] == 1.
  Use date.monthNumbers[name.slice(0,3)] to reverse full names.

attache.date.patterns: Object
  Contains mask patterns for commonly used or standardized date formats:
    ISO8601LongPattern:                "Y-m-d H:i:s"
    ISO8601ShortPattern:               "Y-m-d"
    ShortDatePattern:                  "n/j/Y"
    LongDatePattern:                   "l, F d, Y"
    FullDateTimePattern:               "l, F d, Y g:i:s A"
    MonthDayPattern:                   "F d"
    ShortTimePattern:                  "g:i A"
    LongTimePattern:                   "g:i:s A"
    SortableDateTimePattern:           "Y-m-d\\TH:i:s"
    UniversalSortableDateTimePattern:  "Y-m-d H:i:sO"
    YearMonthPattern:                  "F, Y"

Supported Mask Characters:
  d    day 01-31
  D    day of week, first three letters
  j    day 1-31
  l    day of week
  S    ordinal suffix
  w    day of week 0-6
  z    day of the year, 0-364
  W    ISO week number
  F    month name
  m    month 01-12 
  M    month, first three letters
  n    month 1-12
  t    days in month
  L    leap year, 0 or 1
  Y    4 digit year
  y    2 digit year
  a    am/pm
  A    AM/PM
  g    hours 1-12
  G    hours 0-23
  h    hours 01-12
  H    hours 00-23
  i    minutes 00-59
  s    seconds 00-59
  O    GMT offset
  T    timezone
  Z    timezone offset
  U    seconds since UNIX epoch