BtS: Summary of computations of Turns/Years per different Game Speeds (see file Assets/XML/GameInfo/CIV4GameSpeedInfo.xml for reference).
The Starting Year in BtS is defined in the XML/GlobalDefines.xml file as: START_YEAR = -4000 (read 4000 BC). In the WBS file, you can change it for your scenario with the tag "StartYear=" in the BeginGame section.
In the GameSpeedInfo file, you will find listed all the different phases of the turns/years passing by per speed (GameTurnInfos, made up of iMonthIncrement and iTurnsPerIncrement, see table below).
The Ending Year (for a Time Victory for example) is defined by the Starting Year and the computation of all GameTurnInfos (see table below). In the WBS file, you can change it for your scenario with the tag "MaxTurns=" in the BeginGame section.
You can also enter your scenario at a specific turn/year with the tag "GameTurn=" in the BeginGame section. Usually, you would then adjust the tag "MaxTurns=" accordingly. Example in the AD 1000 scenario: with a GAMESPEED_NORMAL, you reach AD 1000 after 160 turns and 340 turns thereafter, you reach AD 2050 => "GameTurn=160" and "MaxTurns=340".
GAMESPEED_MARATHON
Month Turns Running Total Starting Ending
Phase Increment per Incr. Total Turns Years Year Year
1 180 100 100 1,500 -4000 -2500
2 120 300 400 3,000 -2500 500
3 60 170 570 850 500 1350
4 24 201 771 402 1350 1752
5 12 129 900 129 1752 1881
6 6 180 1,080 90 1881 1971
7 3 264 1,344 66 1971 2037
8 1 156 1,500 13 2037 2050
Total 1,500 6,050
GAMESPEED_EPIC
Month Turns Running Total Starting Ending
Phase Increment per Incr. Total Turns Years Year Year
1 300 140 140 3,500 -4000 -500
2 180 90 230 1,350 -500 850
3 120 40 270 400 850 1250
4 60 90 360 450 1250 1700
5 24 70 430 140 1700 1840
6 12 100 530 100 1840 1940
7 6 220 750 110 1940 2050
Total 750 6,050
GAMESPEED_NORMAL
Month Turns Running Total Starting Ending
Phase Increment per Incr. Total Turns Years Year Year
1 480 75 75 3,000 -4000 -1000
2 300 60 135 1,500 -1000 500
3 240 25 160 500 500 1000
4 120 50 210 500 1000 1500
5 60 60 270 300 1500 1800
6 24 50 320 100 1800 1900
7 12 120 440 120 1900 2020
8 6 60 500 30 2020 2050
Total 500 6,050
GAMESPEED_QUICK
Month Turns Running Total Starting Ending
Phase Increment per Incr. Total Turns Years Year Year
1 720 50 50 3,000 -4000 -1000
2 480 30 80 1,200 -1000 200
3 360 20 100 600 200 800
4 240 30 130 600 800 1400
5 120 25 155 250 1400 1650
6 60 40 195 200 1650 1850
7 24 65 260 130 1850 1980
8 12 70 330 70 1980 2050
Total 330 6,050
Of course, the game adjusts the Months/Years per turn and not just per phase. The more detailed table per turn, I leave it up to you to make it based on these parameters!