Datetime is represented in, so called, external TAI64 format. TAI stands for Temps Atomique International, the current international real time standard. Unlike UTC, it takes leap seconds into account, making it monotonous.
You can convert TAI to UTC by subtracting number of leap seconds.
TAI64N format adds 32-bit big-endian number of nanoseconds (in up to 999999999) count. TAI64NA adds another 32-big big-endian part of attoseconds count.
Shortest form must be used: if number of nanoseconds equals to zero, then use TAI64 format.
Example representations:
| 1970-01-01 00:00:00 TAI | 18 4000000000000000 |
| 1970-01-01 00:00:00 UTC | 18 400000000000000A |
| 1969-12-31 23:59:59 TAI | 18 3FFFFFFFFFFFFFFF |
| 1992-06-02 08:07:09 TAI | 18 400000002A2B2C2D |
| 1992-06-02 08:06:43 UTC | 18 400000002A2B2C2D |
| 1997-10-03 18:15:19 TAI | 18 4000000034353637 |
| 1997-10-03 18:14:48 UTC | 18 4000000034353637 |
| 2016-12-31 23:59:59 UTC | 18 40000000586846A3 |
| 2017-01-01 00:00:00 UTC | 18 40000000586846A5 |
| 2024-11-20 12:19:08 921772500ns UTC | 19 40000000673DD3E136F121D4 |