title: TSQL datetime size
body: <p>I was browsing msdn in regards to data type sizes in T-SQL and noticed something I'm a bit confused on.</p>
  
  <p>According to <a href="http://msdn.microsoft.com/en-us/library/ms186724.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/ms186724.aspx</a>, datetime uses 8 bytes and stores a date from years 1753-9999 with a time precision of hh:mm:ss[.nnn]. Now if you look at date and time separately, time uses 3-5 bytes to store hh:mm:ss[.nnnnnnn] and date uses 3 bytes to store from years 0 - 9999.</p>
  
  <p>What confuses me is that using date and time separately gives you a wider range of years and time with four more digits of precision than datetime, yet they both use 8 bytes? Why does datetime have a smaller range and less precision yet uses the same size to store itself?</p>