[web2py] expression question

[niknok]

I'm wondering why this doesn't work:

    delta=datetime.timedelta(seconds=15*60)
    db(request.now>(db.qa.time_start+delta)).count()

    TypeError: can't compare datetime.datetime to Expression


while this one does:

    delta=datetime.timedelta(seconds=15*60)
    db(db.qa.time_start<(request.now-delta)).count()


Struggled with that line all afternoon, and out of frustration decided
to transpose the values, and suddenly it worked.

/r
Nik