it was likely working fine because you were using a parmater date of 2012 which includes leap day, so as you were converting the your master entry dates to use 2012 as the year all the dates were valid.
Now as you use 2013 in your param, if it finds any entry date of Feb 29 it will fail becasue there is no 2-29-13 (29 is outside the month day range error).
if you use date add it accounts for changing leap day to I believe 2-28. I think dateserial changes it to 3-1.
Below is a formula to use with color coded break dowm of each part. I might have inverted something as I am not at a machine to test the formula out.
1. get the years bewteen the param date and each entry date (purple)
2. add the resulting years to the entry date to make them have the same year value as the param date (red)
3. get the date diff value in days of the param date and the entry date (blue)
4. look ofr that result to be between 1 and 14 (black)
datediff('d',{?date},dateadd('yyyy',datediff('yyyy',{TAEEMASTER.MASTR_ENTRY},{?Date}),{TAEEMASTER.MASTR_ENTRY})) in 1 to 14
Edited by DBlank - 01 Feb 2013 at 3:58am