| Marker | Mnemonic | Epoch | Leap cycle | Leap items | Leap rule |
|---|---|---|---|---|---|
| none | 0001-01-01 | 400 | 1/97 d, 1/71 w | 4:100:400 | |
| by majority of days | |||||
| D | default, date, day Dee-Cecil | 2001-01-01 | 293? | ? | 23:22, 28:34, …? |
| ? | |||||
| F | financial, fiscal | custom | 400 | 5–6/2097 d | 4:100:400 |
| 360-day year aligned with standard count, week unused | |||||
| G | Gregorian, global | 1582-10-15 | 400 | 1/97 d, -02-29 | 4:100:400 |
| weeks begin Sunday, the first Sunday of January starts W01, days before that belong to W00, weeks do not span year boundaries, i.e. they can be partial, dates before the epoch are equal to J. | |||||
| I ≠ 1 | international Indian; Islamic | 2001-01-01 | 293 | 1/71 d, 1/52 w, 1/13 m, 1/4 q | ? |
| inherent | |||||
| J | Julian Jewish | AUC | 4 | 1/1 d | every fourth year a day is added to the last month, i.e. February |
| years begin -03-01 at any day of the week, the standard week cycle is used | |||||
| K | Kalendis | 2001-01-01 | 293 | 1/52 w | distribution as even as possible, 45:79 sub cycles |
| inherent | |||||
| N | no leap, null year; new | 2001-01-01 | 293 | 1/1 y | years have 364 days, every 294th year is year zero of the next cycle which then aligns once again with the 293-year cycle |
| U | user | custom | custom | custom | custom |
| custom | |||||
The markers ‘P’, ‘R’ and ‘T’ are reserved, as is ‘X’, and must not be used. The letters ‘F’, ‘L’, ‘M’, ‘Q’, ‘S’ and ‘W’ should not be used as date markers unless they are semantically compatible with like markers defined herein.
The year count needs to be compatible with the ±CCYY format. This means, among other restrictions, it may not be shorter than 4 digits, except when the cycle length is smaller than 100 years, because YY may be used then. Note, though, that the year count does not have to be purely incremental, i.e. the last three or four digits may be used for counting years of a cycle and then do not necessarily run through 999 or 9999.
