[Zope] What kind of object is bobobase_modification_time?

[Jay, Dylan]

Its acting really weird.
<!--#var "bobobase_modification_time.Date()"--> doesn't work (produces an
attributeError) but
<!--#var bobobase_modification_time fmt=Date--> does.

What I really want to do is
<!--#if "(bobobase_modification_time + 60) > ZopeTime()"-->
but that causes a type error. Doing ZopeTime(bobobase_modification_time)
doesn't work either. I thought bobobase_modification_time was a ZopeTime
object. Whats the story?