[Zope] Using variables in dtml-var fmt attributes

[Nemeth Miklos]

I have string property named df with the value %Y.%m.%d which is a valid
fmt value.
I cannot use this variable in fmt attributes: <dtml-var ZopeTime
fmt="df"> returns an invalid value.
I tried with fmt=df and fmt="_['df']" without any success.
Is there any way to use a variable for fmt attributes?

NM