It can be used to format the date/time of the server .
Example
<?php
echo date(‘Y-m-d :h i’);
?>
Below given are the date formats
d,D,j,l,N,S,w,z,W,F,m,M,n,t,L,o,Y,y,a,A,B,g,G,h,H,i,s,u,e,I,O,P,T,Z,c,r,U
Output
2012-04-25 :11 43