Long term totally agree we need a better plan. I think 

Short term, I think adding both with & without time formats to the list, and looking for a ':' is a reasonable quick-fix?

Right now my focus is on getting a clearer picture around the problems we have with times/dates as opposed to how they are entered - UI can be layered on the top if this PR I think, and having it merged will help us see what TZ related problems we have.