Hi, I have a cross-sectional dataset that contains the company name, company id, and report date. However, some observations may have a report date gap of more than one year and I want to figure out what company has a report date gap of more than one year. I am a beginner in SAS programming...and have no idea how to handle this. Any suggestion....? Thanks.   My orginial dataset look like this:  Name  ID  Rdate AAA 110 31DEC2000 AAA 110 31MAR2001 AAA 110 30JUN2001 AAA 110 30SEP2001 AAA 110 31DEC2001 AAA 110 31MAR2002 AAA 110 30JUN2002 BBB 111 31DEC2000 BBB 111 31MAR2002 CCC 112 31MAR2001 CCC 112 30SEP2001 CCC 112 31DEC2001 DDD 113 31DEC2000 DDD 113 31MAR2001 DDD 113 30JUN2002   Want:  Name  ID  Rdate Gap  AAA 110 31DEC2000   AAA 110 31MAR2001   AAA 110 30JUN2001   AAA 110 30SEP2001   AAA 110 31DEC2001   AAA 110 31MAR2002   AAA 110 30JUN2002   BBB 111 31DEC2000 Y BBB 111 31MAR2002 Y CCC 112 31MAR2001   CCC 112 30SEP2001   CCC 112 31DEC2001   DDD 113 31DEC2000   DDD 113 31MAR2001 Y DDD 113 30JUN2002 Y Y indicates those observations that have a report date gap of more than one year.  ... View more