[web2py] in a db query, why the error: can't compare datetime.datetime to Field

[Luis Goncalves]

Let 

my_DT = datetime.datetime( 2011, 08, 16)


db.define_table( 'entry', Field('DT' = 'datetime' ) )


(and add data records to the database ...) 

 
In a db query, this works:

db( db.entry.DT> my_DT).select()


but this does not: 

db( my_DT< db.entry.DT).select()


producing error :   can't compare datetime.datetime to Field 


Why does that happen?

Thanks,
Luis.