earth time needs some fixes

[Fred T. Hamster]

earth_time:

1. need compares in earthtime
   1. we super need to be able to tell if an earth time is before or after another one.
   2. some kind of calculations based on that would be good also, like to get a magnitude of how far apart two times are and such.
   3. or a difference.
2. need earthtime parsing
   1. we should be able to suck in a text form of a time.
3. need math ops:
   1. want to be able to add / subtract hours minutes etc.
   2. ++ at least, maybe some others might not make as much sense on days or whatever.