Can you tell me specifically what you tried?
I only had 33 journal entries to fix at the time, so I just wrote out the commands by hand in a text editor, and then ran them.
Example, I went to my daily notes directory and ran:
touch -t 202007220130 2020-07-22_Wednesday.md
That sets the date to 2020, 07, 22, 1:30am
If you had 100s of notes you could use Python to format those commands, and then run them automatically. Or have Python print them out, and then run them yourself in your terminal. But I don’t understand where you’re stuck, so I can’t get more specific than that.