Why is the following formula receiving an error?

= 
SUMPRODUCT(--('Spread Sheet'!$A$5:$A$5000 >=date(year($a$4),month(1),day(1)),--($A$5:$A$5000<=$A$4),'Spread Sheet'!$L$5:$L$5000)
For clarification, the target date range and the target data to be summed reside in the sheet entitled "Spread Sheet' whereas the conditional date is in the actual sheet where the formula resides.

Thanks,

Opv