Formatting Email Alerts in Advanced Alert Manager

I am using the ${AlertTriggerTime} variable in my email text.

I want to yield a date in the 24 HR format.

I have tried several format strings such as:

     ${AlertTriggerTime as ShortDate}

     ${AlertTriggerTime as LongDate}

     ${AlertTriggerTime as DDYYHHMMSS}

     ${AlertTriggerTime as YYYY}

     ${AlertTriggerTime as Year}

and they all yield the same result in this format:  6/19/2013 2:21:28 PM

Any suggestions ?