Honestly I feel like it would be easier to just have the "precision" of a date/time be adjustable. Just off the top of my head, ISO8601 is already in the right

Honestly I feel like it would be easier to just have the "precision" of a date/time be adjustable. Just off the top of my head, ISO8601 is already in the right order, just letting users "leave off" anything that's not important and then having a library interpret those "partial dates" as a range internally so it's easy to check identity or if one date is "in" another.