01-01-2010 is interpreted by filemaker as 1 minus 1 minus 2010 = -2010
Try using the Date function in your expressions:
If ( Startdate contract > Date ( 1 ; 1 ; 2010 ) ; Startdate contract ; Date ( 1 ; 1 ; 2010 ) )
Since 2010 is likely not the value you'll want next year, you may want to use Year ( Get ( CurrentDate ) ) in place of 2010 in these expressions.
Note that calculations that refer to get ( CurrentDate ) will not update correctly unless you use storage options to specify that they be unstored.