Period End Date for Leap year

Summary:

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I've created a period end date account. But I'm having trouble getting the leap year functionality to work. It was suggested to use the below formula. FY-Index is an account with a member formula, included below.

 @IF (@CalcMgrIsLeapYear ("FY-Index), 229, 228)

FY-Index = @CalcMgrDoubleFromString (@CONCATENATE ("20", @SUBSTRING (@NAME (@CURRMBR (Years)), 2)))

Error parsing formula for [calc-expression] (line 4): wrong number of arguments in function [@IF]

However, when I put it in, I get errors. I tried removing parenthesis, but no luck. Is there another way to get the February end date to work dynamically?
Full member formula below.