The timefmt SSI directive appears to be ignored by the echo var=DATE_LOCAL directive when the page using SSI is loaded due to a redirection by mod_dir. The problem appears to be in ap_internal_fast_redirect as called on line 159 of modules/mappers/mod_dir.c. Replacing this call with an appropriate call to ap_internal_redirect eliminates the symptoms.
Looks like a dupe of 39369, which has been fixed in 2.2 and trunk. *** This bug has been marked as a duplicate of bug 39369 ***