correct treshold for short year

treshold for short year
0 - 39 > CE 2000 - 2039
40 - 83 > BE 2540 - 2583 > CE 1997 - 2040
84 - 99 > CE 1984 - 1999

treshold for long year
100 - 2399 > CE
2400  - 9999  > BE 2400 > CE 1857 - ????