Convert Time Format

Hi All, 

I need some help with converting my time format. Within the dataset that I have, my time is in 24 hour format  eg. 19:00 and 00:00. I am trying to convert these times into 12 hour format where 19:00 would turn into 7:00pm and 00:00 would turn into 12:00am. 

I used Nominal to Date operator, and set the date type to time, date format to h:mm a, but it's giving me a cannot parse date error since 00:00 is an unparseable date. Any thoughts on solving this problem? 

Thanks!