I've recently had need to search for emails received after a specific time: as in, "After 3pm on the 1st January 2016", and not "After the 1st January 2016".
I disbelieved that this is something Google would neglect to allow for so long. Luckily, I was correct.
You can achieve this if you use the Epoch timestamp instead. For example, to get all emails sent/received since 3pm on the 1st January 2016 (in GMT), all I need to do is search for: