Y2K catches up with me?

[Ano Nimus]

One field: date (which is a field of the type 'date' )

One script:

Show Custom Dialog ["Enter the date" , "Enter the date please" , "date"]

Buttons: "Continue", "Cancel"

Input #1: date

If one enters 1-1-1 on the layout itself and tabs out of the field, the date is 01-01-2001

If one enters 1-1-1 in the custom dialog, the date is 01-01-1901

Does anyone know what's going on? (This is in FMP6)