UTC

My guess at parsing: in effect from 8:53pm UTC on the 13th to 4am UTC on the 14th.

Airplane 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.

Unrolling 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.

And 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.

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.

Friday the 13th at 08:53 PM UTC