Class Date

The date parsing and format syntax is a subset of PHP's date() function, and the formats that are supported will provide results equivalent to their PHP versions. The following is a list of all currently supported formats:

Format  Description                                                               Example returned values
------  -----------------------------------------------------------------------   -----------------------
  d     Day of the month, 2 digits with leading zeros                             01 to 31
  D     A short textual representation of the day of the week                     Mon to Sun
  j     Day of the month without leading zeros                                    1 to 31
  l     A full textual representation of the day of the week                      Sunday to Saturday
  N     ISO-8601 numeric representation of the day of the week                    1 (for Monday) through 7 (for Sunday)
  S     English ordinal suffix for the day of the month, 2 characters             st, nd, rd or th. Works well with j
  w     Numeric representation of the day of the week                             0 (for Sunday) to 6 (for Saturday)
  z     The day of the year (starting from 0)                                     0 to 364 (365 in leap years)
  W     ISO-8601 week number of year, weeks starting on Monday                    01 to 53
  F     A full textual representation of a month, such as January or March        January to December
  m     Numeric representation of a month, with leading zeros                     01 to 12
  M     A short textual representation of a month                                 Jan to Dec
  n     Numeric representation of a month, without leading zeros                  1 to 12
  t     Number of days in the given month                                         28 to 31
  L     Whether it's a leap year                                                  1 if it is a leap year, 0 otherwise.
  o     ISO-8601 year number (identical to (Y), but if the ISO week number (W)    Examples: 1998 or 2004
        belongs to the previous or next year, that year is used instead)
  Y     A full numeric representation of a year, 4 digits                         Examples: 1999 or 2003
  y     A two digit representation of a year                                      Examples: 99 or 03
  a     Lowercase Ante meridiem and Post meridiem                                 am or pm
  A     Uppercase Ante meridiem and Post meridiem                                 AM or PM
  g     12-hour format of an hour without leading zeros                           1 to 12
  G     24-hour format of an hour without leading zeros                           0 to 23
  h     12-hour format of an hour with leading zeros                              01 to 12
  H     24-hour format of an hour with leading zeros                              00 to 23
  i     Minutes, with leading zeros                                               00 to 59
  s     Seconds, with leading zeros                                               00 to 59
  u     Milliseconds, with leading zeros                                          001 to 999
  O     Difference to Greenwich time (GMT) in hours and minutes                   Example: +1030
  P     Difference to Greenwich time (GMT) with colon between hours and minutes   Example: -08:00
  T     Timezone abbreviation of the machine running the code                     Examples: EST, MDT, PDT ...
  Z     Timezone offset in seconds (negative if west of UTC, positive if east)    -43200 to 50400
  c     ISO 8601 date                                                             2007-04-17T15:19:21+08:00
  U     Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)                1193432466 or -2138434463

Example usage (note that you must escape format specifiers with '\\' to render them as character literals):

// Sample date:
// 'Wed Jan 10 2007 15:05:01 GMT-0600 (Central Standard Time)'

var dt = new Date('1/10/2007 03:05:01 PM GMT-0600');
document.write(dt.format('Y-m-d'));                         // 2007-01-10
document.write(dt.format('F j, Y, g:i a'));                 // January 10, 2007, 3:05 pm
document.write(dt.format('l, \\t\\he jS of F Y h:i:s A'));  // Wednesday, the 10th of January 2007 03:05:01 PM

Here are some standard date/time patterns that you might find helpful. They are not part of the source of Date.js, but to use them you can simply copy this block of code into any script that is included after Date.js and they will also become globally available on the Date object. Feel free to add or remove patterns as needed in your code.

Date.patterns = {
    ISO8601Long:"Y-m-d H:i:s",
    ISO8601Short:"Y-m-d",
    ShortDate: "n/j/Y",
    LongDate: "l, F d, Y",
    FullDateTime: "l, F d, Y g:i:s A",
    MonthDay: "F d",
    ShortTime: "g:i A",
    LongTime: "g:i:s A",
    SortableDateTime: "Y-m-d\\TH:i:s",
    UniversalSortableDateTime: "Y-m-d H:i:sO",
    YearMonth: "F, Y"
};

Example usage:

var dt = new Date();
document.write(dt.format(Date.patterns.ShortDate));

//dt = Fri May 25 2007 (current date)
var dt = new Date();

//dt = Thu May 25 2006 (today's month/day in 2006)
dt = Date.parseDate("2006", "Y");

//dt = Sun Jan 15 2006 (all date parts specified)
dt = Date.parseDate("2006-01-15", "Y-m-d");

//dt = Sun Jan 15 2006 15:20:01 GMT-0600 (CST)
dt = Date.parseDate("2006-01-15 3:20:01 PM", "Y-m-d h:i:s A" );

//Basic usage:
var dt = new Date('10/29/2006').add(Date.DAY, 5);
document.write(dt); //returns 'Fri Oct 06 2006 00:00:00'

//Negative values will subtract correctly:
var dt2 = new Date('10/1/2006').add(Date.DAY, -5);
document.write(dt2); //returns 'Tue Sep 26 2006 00:00:00'

//You can even chain several calls together in one line!
var dt3 = new Date('10/1/2006').add(Date.DAY, 5).add(Date.HOUR, 8).add(Date.MINUTE, -30);
document.write(dt3); //returns 'Fri Oct 06 2006 07:30:00'

//wrong way:
var orig = new Date('10/1/2006');
var copy = orig;
copy.setDate(5);
document.write(orig);  //returns 'Thu Oct 05 2006'!

//correct way:
var orig = new Date('10/1/2006');
var copy = orig.clone();
copy.setDate(5);
document.write(orig);  //returns 'Thu Oct 01 2006'

var dt = new Date('1/10/2007');
document.write(Date.dayNames[dt.getFirstDayOfMonth()]); //output: 'Monday'

var dt = new Date('1/10/2007');
document.write(Date.dayNames[dt.getLastDayOfMonth()]); //output: 'Wednesday'