I'm pretty positive that all the dates I have right now are numerical. So, when I apply the code below to specify the year, it gave me only the year, in the past when it was a character, it gave me missing values. Do you get what I mean? Here is the code that I used to only specify the year variable. data EALLB; set EALLA; year=year(DIAG_DT_TM); RUN; ^ this is to prove that I have numeric dates NOT character. but still, I don't know why when I want to merge and match the (visit date), it only gives me 6 observations, which I checked manually and there are a lot of matched dates between the two files. I'm lost. @Reeza
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