Just to head off the inevitable:
yes, the calc is formatted to return text.
yes, the field is set up correctly.
yes, it's a calculation, not an auto-enter calculated value.
The problem isn't with the and operator. The problem is that there are no dates in your expression even though it looks like there is.
1/1/13 evaluates as 1 divided by 1 divided by 13 as the / is the division operator in a FileMaker calculation.
GetAsDate ( "1/1/13" )
Date ( 1 ; 1; 2013 )
in your expressions to refer to a constant date.
Duh, I figured it was something easy that I was overlooking. Thanks.