## 13.6.3.5 GRD

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GRD (Gregorian Date) is a scheme for counting days in a fashion so complicated that it has taken millennia to screw it up. Furthermore, GRD is 'politically incorrect' in that it counts days, not after 'Jesus', but after 'The Lord' (Anno Domini), which is not completely neutral.

But GRD is widespread, and hence we use it in the Human-Computer-Interfaces of Logiweb. In Logiweb itself, GRD has no place.

In GRD, day 0 of a year is named 'January 1', and day 100 is named April 11 (except if the year is divisible by 4, in which case it is named April 10 (except if the year is divisible by 100, in which case it is named April 11 (except if the year is divisible by 400, in which case it is named April 10))).

In Logiweb, Gregorian year Y, month MM, and day DD is written GRD-Y-MM-DD. We have 01 <= MM <= 12 and 01 <= DD <= 31. The notation is compatible with ISO 8601 except for the following: (1) We prepend 'GRD-' to emphasize that we label days like the Gregorian calender does (GRD for GRegorian Date). (2) We allow the year to have more than four digits after year 9999 and to have less then four digits before year 1000. (3) We allow the year to be zero and negative. As examples, GRD-0-01-01 and GRD--5-01-01 are January 1 of year 1 BC and 6 BC, respectively.

When we combine GRD with UTC, then GRD steps at UTC:00:00:00. When we combine GRD with TAI, then GRD steps at TAI:00:00:00. Hence, GRD/UTC and GRD/TAI are two different day counts, but at the time of writing they merely differ by 34 seconds.

Combinations of day and second counting schemes are glued together with a dot. As an example, 0.456 seconds past UTC:12:23:34 on GRD-2000-01-01 is written GRD-2000-01-01.UTC:12:23:34.456. This follows ISO-8601 in putting the day before the second but does not follow the suggestion of ISO-8601 to separate day and second by a capital 'T'.

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