[R] Convert H:MM:SS PM /AM into 24 HR syntax

[Jason Rupert]

I've got an array of times in H:MM:SS PM/AM format, e.g. "5:27:15 PM" (no leading zero), and I would like to convert them over to 24 HR syntax, e.g. HH:MM:SS.

If it matters, the times are from the Central Time zone. 

Is there a command to convert the time to a 24HR format? 

I tried the following: 
ptime("5:27:15 PM", "%H:%M:%S")
[1] "2009-11-04 05:27:15"
> strptime("5:27:15 PM", "%h:%M:%S")
[1] NA
> strptime("5:27:15 PM", "%R:%M:%S")
[1] NA
> strptime("5:27:15 PM", "%r:%M:%S")
[1] NA
Note that the top one is incorrect due to it not using the "PM" indicator.

Thank you for any insights any feedback that can be provided.