Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

1. Change the modifiled timestamp of a file to the specified timestamp.

   touch -m -t 201512180130.09 some_file
   

2. Change the modified timestamp of a file to the current time.

   touch -m some_file
   

3. Change the modified timestamp of all files in the current directory to the current time.

   find . -type f -print0 | xargs -0 touch -m
   

4. You can use the stat command to show the modified timestamps of files.

   stat -c '%y' some_file
   

References

https://unix.stackexchange.com/questions/118577/changing-a-files-date-created-and-last-modified-attributes-to-another-file