600 turn advancements: 20*100+70*50+75*20+65*10+60*5+70*2+60*1+60*6/12+60*3/12+60*1/12=8200; transitions at 4000 and 500 BC, and at 1000, 1650, 1950, 2090, 2150, 2180, and 2195 AD.
900 turn advancements: 90*50+95*20+90*10+100*5+110*2+95*1+100*6/12+100*3/12+120*1/12=8200; transitions at 1500 BC and at 400, 1300, 1800, 2020, 2115, 2165, and 2190 AD.
1200 turn advancements: 50*50+145*20+150*10+150*5+140*2+145*1+160*6/12+140*3/12+120*1/12=8200; transitions at 3500 and 600 BC, and at 900, 1650, 1930, 2075, 2155, and 2190 AD.
1500 turn advancements: 20*50+190*20+180*10+180*5+180*2+180*1+190*6/12+200*3/12+180*1/12=8200; transitions at 5000 and 1200 BC, and at 600, 1500, 1860, 2040, 2135, and 2185 AD.
1800 turn advancements: 200*20+220*10+230*5+215*2+225*1+230*6/12+240*3/12+240*1/12=8200; transitions at 2000 BC and at 200, 1350, 1780, 2005, 2120, and 2180 AD.
2400 turn advancements: 100*20+330*10+320*5+345*2+335*1+330*6/12+340*3/12+300*1/12=8200; transitions at 4000 and 700 BC, and at 900, 1590, 1925, 2090, and 2175 AD.
3000 turn advancements: 450*10+410*5+430*2+430*1+440*6/12+420*3/12+420*1/12=8200; transitions at 1500 BC and at 550, 1410, 1840, 2060, and 2165 AD.
3600 turn advancements: 350*10+520*5+550*2+540*1+560*6/12+540*3/12+540*1/12=8200; transitions at 2500 BC and at 100, 1200, 1740, 2020, and 2155 AD.
4800 turn advancements: 150*10+750*5+760*2+770*1+790*6/12+800*3/12+780*1/12=8200; transitions at 4500 and 750 BC, and at 770, 1540, 1935, and 2135 AD.
These turn length quantities were made to ensure constant "normal-looking" dates, only one outlier (the earliest one) in terms of quantities of turns at each turn length, and a low standard deviation for the non-outlier turn quantities (for regularity per turn length quantity after you pass the outlier).