If statement to add 1 if false

[rs1aj]

Trying to build pivot table to give me true TY vs LY sales numbers. Today is Tuesday 6/9/2015, LY the same Tuesday was 6/10/2014. I have the date broke up in to individual columns...one for month, day, year. I'm trying to add a column that will return the current value in the @Day field if @Ship Date is this year, and return the (current value + 1) in the @Day field if @Ship Date is last year. Below is not working.

=IF(YEAR([@[Ship Date]]="2015"),[@Day],([@Day]+1))

[rs1aj]

Just remembered this is going to be a problem with the last day of every month.

Anyone have any suggestions how to get a pivot table to pull in the right sales figures vs LY for each day?