Re: [tied] Ancient Egyptian calendar problems

They Egyptians had a very good calendar by the Roman period, and the problem
of "wandering" had been solved - Julius Caesar pinched the idea of leap
years from it.

I don't believe it is the case that "all cultures" had solved this problem,
or even that they knew the year was 365 and a bit days long. The Roman
calendar was two months short at one stage, and was six months out when
Julius Caesar revised it. The priests used to insert an entire month when
they deemed it right - which meant when they liked whoever was in power.
The classical Greeks likewise had not solved the problem of how long the
year is, though later Greek science was able to establish a whole bunch of
stuff (such as precession of the equinoxes) better than astronomers in the
1800's.

The modern Islamic claendar is strictly lunar, which means it does not
pretend to follow the sun or the seasons. It is 11 days shorter than the
solar calendar, so Ramadan moves forward 11 days each year. Interestingly,
the year 200 had Ramadan twice, once very early in January, the other very
late in December. The month changes only when the new moon can actually be
seen at Mecca, so dating in advance is never quite certain.

The modern Hebrew and Sikh and Hindu calendars are a compromise, with
certain festivals or events fixed within a range (a bit like Easter is in
the Christian religious calendar), so that Autumn festivals occur in Autumn
and so on.

Hope that helps
Peter