Why isn't "like" appropriate?

As has been said, a useful LIKE statement needs wildcards (otherwise it's just testing equality). Not to stray too far OT, but you'd also need to cast your date to a string (using to_char). Basically, my advice (for what it's worth) is to stick with comparisons like <= for dates.

The part about the nls setting is more important. You should insure that your DBIx connection spits out dates in the same format as your other Oracle clients. Who knows, you could be trying to compare these to ISO 8601 format.