I say "loose" because while this new calendar had 365 days and its 30-day and 31-day months no longer accurately tracked the phases of the Moon, the Romans clearly weren't too bothered about overly precise timekeeping. For one thing, there were only ten months, which correspond to the modern March through December and totaled 304 days of the year.
This, incidentally, is why the ninth through twelfth months have names - September, October, November, December - that derive from the Latin words for seven through ten. Those once were their positions in the Roman calendar. The end of the year between the final month December and first month March belonged to no specific month. This might seem like horribly shoddy timekeeping, but the early Romans were primarily concerned with practical questions of the harvest. The wintry period between December and March didn't factor into the harvest, so what was the point of assigning specific months to describe them?
The full mnemonic is "Thirty days hath September/April, June and November/All the rest have thirty-one/except February alone/which has eight and a score/until leap year gives it one day more."
D - just to make it even less helpful, the etymological # basis for the months does not even coincide with what month they are. I found this one out the hard way. This past year, I had to renew my guard license. I somehow thought September was month 8 and not 9. My brain assumed September was month 8. This nearly made me unable to work as I rushed to complete the renewal at the last minute.
D - this is how I started thinking about expanding a # system to a base-12 instead of base-10. I expand on the simple and rational naming conventions in this fashion. Instead of needing to denote 11 and 12 with a 10+1 and +2 system, the base-16 hexadecimal system allows equal ease into double digits. Note that the English tradition refers to 12 as a dozen, and 20 as a score. Eleven and twelve both has unit 'single digit' style names, unlike the much more regular "-teen" from 13 to 19. The similarity of the 'teen' sound to 'ty' for 20s is most unfortunate.
D- aside: days of the week.
Germanic - from old English.
Sunday - sun. Monday - moon. Tuesday - Norse god Tyr. Wednesday Wodan (Odin). Thursday - Thor. Friday - goddess Frige. Saturday - Saturn, associated with Greek titan and progenitor of their gods, Cronos.
Haha ... TGIF! It's GODDESS day! Yessirreee.