The ISO 8601 format may be used with the Gregorian and the Julian systems, as well as many others.

3.3.1 Representing Dates

The ISO 8601 offers numerous choices when formatting dates. The Essential Tools Module supports all calendar dates and formats, with the exception of expanded formats.

3.3.1.1 Complete Extended Format

3.3.1.2 Ordinal Dates Format

The 8601 standard also allows formatting dates based on the ordinal week or the ordinal day, rather than the month, as follows:

• YYDDD, YY-DDD

  This is a two-digit year followed by year-day number.

  Example: 67-256 corresponds to 09/13/1967

• YYYYDDD YYYY-DDD: four-digit year followed by year day number

  Example: 1967-256 corresponds to 09/13/1967

• -DDD year day number

  ---

  Note: all dates starting with dashes indicate truncated dates/times with default values that are implicitly agreed upon by the -participants in the data transfer. Currently, the current date/time values are used whenever a truncated date or time is encountered.

  ---

• YYYY-Www-D YYYYWwwD: Four-digit year followed by week number and week day number

• YYYYWww YYYY-Www: Four-digit year number followed by week number

• YYWwwD YY-Www-D: Two-digit year, week number and week day number

• YYWww YY-Www: Two-digit year, week number

• -YWww -Y-Www: One-digit year, week number

• -WwwD -Www-D: Week number and week day number in default year

• -Www: Week number; default year and week day number

• -W-D: Week day number in default year and week number

  Note that the week number is calculated with first week of the year which is 1. The first week of the year is the first week which contains a Thursday. Thus, the first week of the year 1994 is not the week containing the 1st of January but rather the week 03/01-09/01/1994. Year 2004 is an example of a year that has 53 ISO8601 weeks since it contains both the week containing 1st of January and the week containing 31st of December.

3.3.2 Representing Times

The complete extended format for representing time is:

HH:MM:SS

where HH is the hour, MM is the minute, and SS is the second. The time string may carry a leading "T" as in:

THH:MM:SS

The leading T may appear even when the time string is not a part of a date-time string. For example:

16:59:59 (Hour 16, minutes 59, seconds 59) or

T16:59:59

Using the same basic format, you may omit the colons (:) as follows: 165959.

For truncated representations, you may omit the seconds and/or minutes.

Example:

• 23:59 for 23:59 and zero seconds

• 23 for the hour 23 with zero minutes and zero seconds

3.3.2.1 Applying the ISO Standard to Time Zone Offsets

Specifying other times: For time zone offsets east, or ahead of, UTC time, use the notation+/-HH:MM where "HH" is the hour and "MM" is the minute. For time zone offsets west, or behind, UTC time, use the notation "-HH:MM", "-HHMM", or" -HH".

Be careful when specifying times as offsets of UTC. Offsets are strictly the number of minutes and seconds offset from UTC. For this reason, a time zone may be represented as an offset from UTC in addition to the application of Daylight Saving Time (DST) rules.

3.3.3 Putting Dates and Times Together

3.3.4 Omitting Elements of a Date or Time String

Table 3: Calendar dates

Table 4: Ordinal dates

Examples of combined date-time formats:

• -12-24T-59:59 represents December 24th of the current year; and 59 minutes and 59 seconds into the current hour.

• --24T--59 represents the 24th day of the current month in the current year; and 59 seconds into the current minute in the current hour.

3.3.5 Complete List of Supported Formats