Since I can not go out, I spend everyday with Keyboard Maestro. It's really a good APP 
I don't have experience with csv file. But if the line is like “7:00 am - 9:00 pm”.
You can use “search Using RegEx” macro in KM to extract first Time and last Time.
Problem 1: Extracting Time String From the Line
You can use "search using RegEx" macro.
the RegEx should be:(((\d|\d\d):\d\d)( )(am|pm))( - )(((\d|\d\d):\d\d)( )(am|pm))
Problem 2: Convert 12 Hour Time to 24 Hour Time
Refer the page:
https://macscripter.net/viewtopic.php?id=35417
MacScripter / How to convert 12hour format to 24 hour format?
Refer the code on the page, and edit it to fit our case:
Now we got our final KMM. It works good on my machine(KM Version 9.0.4@MacOS10.12.6).
You can use "For each" macro in KM to do the conversion line by line.
Hope it helps.
ANSWER convert 12hour time to 24 hour time v0_Backup_20200326_0955_v0_Backup_20200326_0955_v0.kmmacros (7.5 KB)