Is there a way of converting "2013:05:19 13:45:45" into a unix time stamp?
Convert time
strtotime();
or
(new DateTime('2013:05:19 13:45:45'))->format('U')
5 days later
I would point out that "2013:05:19 13:45:45" is going to result in a different time stamp depending on which time zone it happens in. If you see that on your clock in New Zealand, it's a very different time stamp than one would get in London, for instance. The PHP [man]DateTime[/man] and [man]DateTimeZone[/man] classes will be very useful if you want to get precise about it.
a month later
php date time code examples on php date time