The information presented here is a quick reference adapted from Wikipedia’s ISO 8601 article to describe the formats used in this site.

Dates and Times

Dates are presented in YYYY-MM-DD format.

Times are presented in 24-hour hh:mm format. The specification includes a leading T character, but it is omitted here. The specification also permits the omission of minutes if a time occurs at the “top of the hour,” but doing so can lead to confusion; so minutes are included with all formatted times.

When combined, the date and time elements are separated by a space to improve readability, i.e., YYYY-MM-DD hh:mm, rather than the specified T character.

Timezones

Times are typically represented in local time, which for this site is Central Time (UTC-06:00, or UTC-05:00 during Daylight Savings Time).

However, if specific time zone information is important for some reason, then times will likely include the offset suffix, e.g., -06:00, or be given in UTC with a Z suffix.

For example, 2023-03-05 12:00 can be considered equivalent to 2023-03-05 12:00-06:00 and 2023-03-05 18:00Z.

The use of a - character for this information necessitates a seemingly odd format for encoding intervals.

Weekdays

Weekdays are not mentioned in the official ISO 8601 specification outside of using a “week-numbering year,” but if they are included as part of the content in this site, they will be either:

1. mentioned before the date, e.g., Sunday, 2023-03-05 12:00; or

2. abbreviated after the date, e.g., 2023-03-05 (U) 12:00.

The abbreviations that might be used:

Durations

Durations are not commonly used in the content of this site, but they are included here for completeness.

This is probably best explained and understood using several examples:

• 3 years: P3Y
• 1 month: P1M
• 3 years, 1 month: P3Y1M
• 30 minutes: PT30M
• 3 years, 1 month, 30 minutes: P3Y1MT30M
• 24 hours: PT24H
• 1 day: P1D
• 6 weeks: P6W
• 10 seconds: PT10S
• 1 year, 2 months, 3 weeks, 4 days, 5 hours, 6 minutes, 7 seconds: P1Y2M3W4DT5H6M7S

In general, P<date>T<time>, where <date> and <time> contain “atoms” according to the specified time unit with a preceding count. Atoms are ordered with the largest unit first, and atoms without any value are omitted.

• <date> atoms are:
  • Y for years
  • M for months
  • W for weeks
  • D for days
• <time> atoms are:
  • H for hours
  • M for minutes
  • S for seconds

Intervals

Intervals represent ranges of that are anchored to a specific date and/or time (either at the start, at the end, or both). If either the start or the end is not a date/time, then a duration is used instead.

The specification defines intervals using the following format options:

1. <start>/<end> - anchored with date/time on both sides,
2. <start>/<duration> - anchored with a start date/time and duration following, or
3. <duration>/<end> - anchored with an end date/time and duration preceding.

The first format is almost exclusively used in the content on this site. This format permits the omission of higher-ordered elements (i.e., those with larger units) that are identical between the start and end. For example:

• 2023-03-05 12:00/2023-03-05 16:00 can be shortened to 2023-03-05 12:00/16:00
• 2023-03-05/2023-03-07 can be shortened to 2023-03-05/07