I really need to stop posting stupid questions like this. I post them, and then play around with the editor and test it, and end up answering my own question half the time.
Default time progression goes like this:
1 4000 BC to 2750 BC 50 years each turn, 25 turns (1-25 turns)
2 2750 BC t0 1750 BC 40 years each turn, 25 turns (26-50 turns)
3 1750 BC to 750 BC 25 years each turn, 40 turns (51-90 turns)
4 750 BC to 250 AD 20 years each turn, 50 turns (91-140 turns)
5 250 AD to 1250 AD 10 years each turn, 100 turns (141-240 turns)
6 1250 AD to 1750 AD 5 years each turn, 100 turns (241-340 turns)
7 1750 AD to 1950 AD 2 years each turn, 100 turns (341-440 turns)
then at 1950 or so it gives a message that the game officially ends in .... (whatever it is). So to slow down the last part of the time progression I just need to change it to 200 turns at 1 unit (in this case years) per turn.