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.

You'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 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.