ISO 8601-2:2019 pdf download – Date and time – Representations for information interchange
5.4.1 General
Grouped time scale units can be applied to date and time representations as replacements for any time scale unit components as long as the resulting expression is a valid one. EXAMPLE 1. ‘2018Y4G60DU6D’ is a valid date expression that refers to the date year 2018, 6th day of the 4th 60-day group, which is the 186th ordinal day of year (in the Gregorian calendar, the 186th ordinal day is July 5th in a common year and July 6th in a leap year). EXAMPLE2 ‘2018Y9M2DT3GT8HU0H30M’ is a valid date and time expression that refers to the date year 2018, September 2nd, 16:30 (30 minutes into the third 8-hour period). While the inner expression ‘0H is supplied, it can be omitted in accordance with 7.10. EXAMPLE3 ‘2018-02-2G14DU’ (implicit form) and ‘2018Y2M2G14DU’ (explicit form) are complete date expressions that indicate “the second fortnight of February 2018”, as specified by the rule “group every 14 days, second group”. EXAMPLE4 ‘2018-03-3G10DU’ (implicit form) and ‘2018Y3M3G10DU’ (explicit form) are complete date expressions that indicate “the third 10-day block of March in 2018”, as specified by the rule “group every 10 days, third group”. A 10-day block is a time grouping commonly used in East Asia. EXAMPLE5 ’16:1GT15MU’ (implicit form) and ‘T16H1GT15MU’ (explicit form) are time expressions that indicate “the first quarter-hour of 16:00”, as specified by the rule “group every 15 minutes, first group”. EXAMPLE6 ‘2018-1G6MU’ (implicit form) and ‘2018Y1G6MU’ (explicit form) are date expressions of six- monthly precision that indicate “the first half of 2018”, as specified by the rule “group every 6 months, first group”, and therefore the grouping is specified in the [month] field. The resulting time interval is equivalent to the time interval expression 2018-01-01/2018-06-30′ and the sub-year grouping expression ‘2018-40′.
5.4.5.1 General
When an expression referring to a grouped time scale unit has to be converted to use basic time scale units (time scale units that are defined in 4.3 and ISO 8601-1:2019, 4.3), it can be converted into a time interval. EXAMPLE 2018Y1G6MU’ refers to the first 6-month group of year 2018. The resulting time interval is equivalent to that of the time interval expression ‘2018Y1M/2018Y6M’.
5.4.5.2 Truncation of partial units
When the duration of a grouped time scale unit does not cleanly divide the original time scale component, the last unit of the grouped time scale is only partially within the boundaries specified by the original time scale component. In this case, the particular grouped time scale unit refers only to the duration that is within bounds of the original time scale component. The remaining duration that are out of bounds shall be truncated. EXAMPLE ‘2018Y9M4G8DU’ refers to the “fourth 8-day grouping of September of the year 2018”, but the fourth grouped unit only has 6 days within September (2 days are in October). According to the above truncation rule, only the first 6 days belong to this grouped unit, and the resulting time interval is 2018-09-25/2018-09-30′.
5.4.5.3 Spanning grouped unit boundaries
In order to express a time interval covered by the grouped unit without regard to the boundaries of the original time component, the same expression can be provided using time interval representation. EXAMPLE . For ‘2018Y9M4G8DU’ (“fourth 8-day grouping of September of the year 2018”), the start date of the fourth grouped unit can be found as ‘2018Y9M25D’. Therefore, the expression of ‘2018Y9M25D/ P8D’ provides the full 8-day duration of the unit, in the interval ‘2018Y9M25D/2018Y10M2D’.