Following up on Joseph Coveney's suggestion that the value of Year that looks like "1990" might contain additional non-numeric characters that do not display, a more specific diagnosis of the problem could be achieved by
charlist Year if missing(real(Year))
I also agree with Nick Cox that it sounds like what you really want is best achieved with -destring- rather than using the date() function. The above applies in either case, though.
Hope this helps.
Clyde Schechter
Dept. of Family & Social Medicine
Albert Einstein College of Medicine
Bronx, NY, USA
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