It's a format called "Date-Time Group" (DTG). Used in military, I think it dates back to teletypes, and is better to say over radio than modern ISO formats.
replyYou'd say "Valid from the thirteenth at two zero five three zulu" over radio.
The TLDR is that punchcard operators found the DTG date format convenient. Punchcard sorting is easiest when the consecutive bits encode the sort key, and the DTG format is easy to split into different sets of bit ranges corresponding to common business logic.
replyAirplane software is some of the oldest on the planet, pre-dating anything that would be considered a best practice. When you see something weird in the space, assume it is because someone in the 1960s thought using more than two characters world be a profligate waste of space.
replyUnrolling these decisions is a monumental task given the decades of hardware already deployed in the field that will only be upgraded when the current unit fails.
> When you see something weird in the space, assume it is because someone in the 1960s thought using more than two characters world be a profligate waste of space.
replyAnd with 1960s technology, this might just have been a very reasonable decision.
Totally. Just some of those decisions put awkward constraints when the hardware is now a million times more capable.
replyMy guess at parsing: in effect from 8:53pm UTC on the 13th to 4am UTC on the 14th.
replyFriday the 13th at 08:53 PM UTC
replyUTC
reply