Fix for Bug 8337 alternate way

Currently the issue is Zend Date doesn't handle AM/PM well which is
actually a default of SilverStripe's time formatting so by first
converting the time via PHP into military we can ensure that conversion
will be write when casting into zend.

Example tests that are failing -

Zend_Date('12:00AM', 'HH:mm:ss') = 64800 seconds which = 1/1/1970
12:00:00 PM, 12:00PM != 12:00AM.  Trying to find if this is a bug with
Zend_Date but unable to find anything.