How to display a maximum time value

I could use a little help in getting a maximum time value to display correctly.

In a form I have several ENDTIME values where I want to have a field look at the list (ENDTIME0, ENDTIME1, ENDTIME2, ENDTIME3, ENDTIME4, ENDTIME5) and display the highest value in the field ENDDEPOSITIONTIME.

In ENDDEPOSITIONTIME, I have the Calculation Value to look at all of the EndTimes listed above and I'd like to see the highest value displayed.

• All of the ENDTIMEx have the format as h:MM tt so they display as 4:08 pm.
• ENDDEPOSITIONTIME when formatted as h:MM tt, throws an error "The value entered does not match the format of the field ENDDEPOSITIONTIME" 
• When I change the format to NONE, the result I get is 4.08. That's the correct answer for this example, but the format is not correct. The result does not have the colon or the am/pm.

Any help would be appreciated for this newby Javascript writer.