Can't find the posts as the strategy section doesn't seem to be working properly, but here's some info:
The main info post is here (it's enormous)
http://www.civfanatics.com/civ3infocenter.shtml
This was cut and pasted from it (better displayed in the original)
Years Per Turn Figures (Total # of Turns = 540):
If youve wondered how the years/turns equation works here are the figures. They can be handy to know if youre trying to work out how many turns you have left in a quest for a culture victory, how many turns you need before a particular Temple (or whatever) gets its 1000 year bonus, or just to see how many turns you have left to achieve your objectives. It seems the Year/Turn figures don't vary with difficulty level.
Period Years Per Turn Turns
4000 BC - 2750 BC 50 25
2750 BC - 1750 BC 40 25
1750 BC - 750 BC 25 40
750 BC - 250 AD 20 50
250 AD - 1250 AD 10 100
1250 AD - 1750 AD 5 100
1750 AD - 1950 AD 2 100
1950 AD - 2050 AD 1 100
And (according to some scribbled notes on my notepad) this is how the same figures look if you're trying to see how many turns per 1,000 years (which is handy if you're trying for a culture victory as culture buildings double their points when they've stodd for 1,000 years).
4000 - 3000 BC = 20 turns
3000 - 2000 BC = 24 turns
3000 - 1000 BC = 36
1000 - 000000 = 48
0000 - 1000 AD = 87
1000 - 2000 AD = 275
2000 - 2050 AD = 50
Excuse crummy layout. Hope it helps.