Steps for custom relabeling jpg files using MyRenamer. 
(1) Copy all the jpg files you want to relabel with the same correction into a separate folder called SpecialCases here.  Folder SpecialCases is in the top-level folder All Camera Trap Data (or whatever you called it)
(3) Double-click on MyRenamer
(5) Type the name of the folder containing the files to be renamed (here I type SpecialCases)  
(6) Type all 6 numbers each separated by a space that you want to add to each jpg file.  For example, to add 1 year, 3 months, 5 days, 10 hours, leave minutes unchanged, and add 20 seconds to the date and time enter: 1 3 5 10 0 20.  All fields must be >0 and <= their limits: months <= 12, days <= 31, hours <= 24, minutes & seconds <= 60.  Note that all changes carry-forward.  That is, an offset of 12 hours added to a camera trap showing 15 hours results 
in the hour being set to 27 hours = 3 hours, plus 1 additional day.  If the day increases past the month then the month is increased by 1. All six numbers must be entered with spaces between the.  Then ENTER.
(7) Let MyRenamer run to completion. Open and inspect outMyRenamer.txt.  The relabeled files are in folder SpecialCases