For that approach to work, wouldn't you have to add 306 days to both the birthdate and the present time before using the Year and DayOfYear properties? The notion that someone born on 2/28/2000 would have had to wait 366 days to be "one year old", while someone born on 3/1/2000 would only have to wait 365 days, is somewhat artificial but it is certainly well-established. #2/28/2000#.DayOfYear == 59 #2/28/2001#.DayOfYear == 59 #3/1/2000#.DayOfYear == 61 #3/1/2001#.DayOfYear == 60 #2/28/2000#.AddDays(306).DayOfYear == 365 #2/28/2001#.AddDays(306).DayOfYear == 365 #3/1/2000#.AddDays(306).DayOfYear == 1 #3/1/2001#.AddDays(306).DayOfYear == 1 Of course, adding 306 days has an ugliness all its own. My own preference would probably be to simply format the thing as MMDDHHMMSS, do a string compare, and adjust the year appropriately, but another option would be to format as YYYYMMDDHHMMSS, convert to a long or double, subtract, and divide by 10,000,000,000.