does anyone know what variable replaced v1.2 variable, ${DATETIME}, in asterisk 1.4
STRFTIME is the replacement function for it. A good link for this is:
voip-info.org/wiki/index.php … c+strftime
It gives the various flag definitions in there.
Personally, I use ${STRFTIME(${EPOCH},%Y%m%d-%H%M%S)}, just as an example.
Hope this helps 
in the source directory there is a document called UPGRADE.txt
have a read of it.