Thank you for posting the data.  When I imported the data into SAS, I noticed there were some problems since it was interpreting the year 98 as 2098 rather than as 1998.  I tried to make corrections and then got an error message that there was not sufficient data.  I checked again and had missed one of the incorrect year values, so I made the correction and was able to generate results using different values for Time Length.  You might need to check how the imported date values are being imported by SAS.  I would have expected an error rather than a green tick mark if that were the case though.     I hope this helps! Doug ... View more