Hello Varaonaid,
I had that problem too when I first switched to Linux Mint from Win 7. I wrote a very long text about that period (
Transition from Win7 to LinuxMint my first month) but you don't need to read that post since this is the excerpt that concerns your question of batch changing the time stamps inside a folder and it's subfolders and all of the files therein to one particular time stamp.
this was the code from Terminal
$ find -print | while read filename; do
> touch -a -m "2020-01-13 15:00:00" "$filename;
> done
Just make sure you run it from Terminal opened inside the Folder where you want to change everything to the same time stamp (with all files and subfolders recursively). The given format was needed for Linux Mint (put your own date and time instead as this only serves as guideline), even some of the formats mentioned in man touch pages did not produce any result so I give one format that was accepted.
But before I switched all my files and folders to the same time stamp I first used FreeFileSync with option to check for file content while comparing source and target folders and made sure these are properly synced I kept using FreeFileSync after that but with option to just check for file size and time stamp (works way faster once you are sure you lose nothing). Whenever I have two options to do the same thing both from the Terminal and from a GUI application, I always choose the GUI but it's up to you.
Separate topic when you are syncing folders is also to make sure that PCs on both ends of the syncing process use same time synchronization (either from a Network Time Server or Local Server who can serve as a time server. You will find a lot of posts yourself if this should be needed.
