When creating a moment from a string, we first check if the string matches known ISO 8601 formats, we then check if the string matches the RFC 2822 Date time format before dropping to the fall back of new Date(string) if a known format is not found.

var day = moment("1995-12-25");

Warning: Browser support for parsing strings is inconsistent. Because there is no specification on which formats should be supported, what works in some browsers will not work in other browsers.

For consistent results parsing anything other than ISO 8601 strings, you should use String + Format.

Supported ISO 8601 strings

An ISO 8601 string requires a date part.

2013-02-08  # A calendar date part
2013-02     # A month date part
2013-W06-5  # A week date part
2013-039    # An ordinal date part

20130208    # Basic (short) full date
201303      # Basic (short) year+month
2013        # Basic (short) year only
2013W065    # Basic (short) week, weekday
2013W06     # Basic (short) week only
2013050     # Basic (short) ordinal date (year + day-of-year)

A time part can also be included, separated from the date part by a space or an uppercase T.

2013-02-08T09            # An hour time part separated by a T
2013-02-08 09            # An hour time part separated by a space
2013-02-08 09:30         # An hour and minute time part
2013-02-08 09:30:26      # An hour, minute, and second time part
2013-02-08 09:30:26.123  # An hour, minute, second, and millisecond time part
2013-02-08 24:00:00.000  # hour 24, minute, second, millisecond equal 0 means next day at midnight

20130208T080910,123      # Short date and time up to ms, separated by comma
20130208T080910.123      # Short date and time up to ms
20130208T080910          # Short date and time up to seconds
20130208T0809            # Short date and time up to minutes
20130208T08              # Short date and time, hours only

Any of the date parts can have a time part.

2013-02-08 09  # A calendar date part and hour time part
2013-W06-5 09  # A week date part and hour time part
2013-039 09    # An ordinal date part and hour time part

If a time part is included, an offset from UTC can also be included as +-HH:mm, +-HHmm, +-HH or Z.

2013-02-08 09+07:00            # +-HH:mm
2013-02-08 09-0100             # +-HHmm
2013-02-08 09Z                 # Z
2013-02-08 09:30:26.123+07:00  # +-HH:mm
2013-02-08 09:30:26.123+07     # +-HH

Note: Support for the week and ordinal formats was added in version 2.3.0.

If a string does not match any of the above formats and is not able to be parsed with Date.parse, moment#isValid will return false.

moment("not a real date").isValid(); // false

The RFC 2822 date time format

Before parsing a RFC 2822 date time the string is cleansed to remove any comments and/or newline characters. The additional characters are legal in the format but add nothing to creating a valid moment instance.

After cleansing, the string is validated in the following space-separated sections, all using the English language:

6 Mar 17 21:22 UT
6 Mar 17 21:22:23 UT
6 Mar 2017 21:22:23 GMT
06 Mar 2017 21:22:23 Z
Mon 06 Mar 2017 21:22:23 z
Mon, 06 Mar 2017 21:22:23 +0000
  1. Day of Week in three letters, followed by an optional comma. (optional)
  2. Day of Month (1 or 2 digit), followed by a three-letter month and 2 or 4 digit year
  3. Two-digit hours and minutes separated by a colon (:), followed optionally by another colon and seconds in 2-digits
  4. Timezone or offset in one of the following formats:
  5. UT : +0000
  6. GMT : +0000
  7. EST | CST | MST | PST | EDT | CDT | MDT | PDT : US time zones*
  8. A - I | K - Z : Military time zones*
  9. Time offset +/-9999

[*] See section 4.3 of the specification for details.

The parser also confirms that the day-of-week (when included) is consistent with the date.