If you need to calculate age in days using SQL Server Transact-SQL, you have lots of options. When your age should be displayed in elapsed "days" for example, you might think that using the DAY attribute in DATEDIFF() would be the way to go. But you may want to use HOUR rather than DAY if your calculations must be accurate. Why?  Because with DATEDIFF() using DAY, calculations are based on midnight boundaries. This means that your number of days will change if you are before or after the midnight boundary. For example, your actual time-span may have only been a couple of hours  … [Read more...]