Unix Timestamp Searching

[eluser]pgsjoe[/eluser]
So I thought I had an idea of how to do this, but now I'm just lost. I've got my submitDate field in my database as a Unix Timestamp. But now, I need to search for submissions that are only from April. So how do I search a Unix Timestamp for a month, when it's not written as 04 in the timestamp? Thanks in advance.