How to turn string Date/Time into something usable

Thank you everyone! This has been very helpful!

I'm now trying to get the hour to be in 24 hour format.
The problem I'm having is that I don't know how to ADD two numbers together.
I end up concatenating them together.

I'm using this line in a CASE statement:
WHEN 'PM' THEN toInteger(dt4[0]) + 12
This results in:
"2019-09-29T812:51"

I have been scouring the Cypher manual but I can't find a way to do this.
Any thoughts?

J