Set directory timestamps to most recently modified file within (recursively)

How do I change the timestamp of a directory and all the sub-folders within that directory to reflect the modification times of the contained files? For example with this directory structure: [Jan 9] root ├── [Jan 3] file1 ├── [Jan 7] file2 ├── [Jan 6] sub1 │   ├── [Jan 2] file3 │   └── [Jan 1] file4 └── [Jan 4] sub2 └── [Jan 8] file5 Here is a one liner to generate that: mkdir -p root/sub1 root/sub2 && touch -d '2018-01-08' root/sub2/file5 && touch -d '2018-01-04' root/sub2/ && touch -d '2018-01-01' root/sub1/file4 && touch -d '2018-01-02' root/sub1/file3 && touch -d '2018-01-06' root/sub1/ && touch -d '2018-01-07' root/file2 && touch -d '2018-01-03' root/file1 && touch -d '2018-01-09' root/ It can be listed with tree -D I'd like to change the timestamps on the three directories to be: [Jan 8] root ├── [Jan 3] file1 ├── [Jan 7] file2 ├── [Jan 2] sub1 │   ├── [Jan 2] file3 │   └── [Jan 1] file4 └── [Jan 8] sub2 └── [Jan 8] file5 Note: - The current timestamps on the directories are completely ignored and the new time stamps are set only based on the contents. - Time stamps bubble up to multiple levels of parent directories. The reason that I'm doing this is for a directory that gets copied with rsync. The directory is checked into git and could get rsynced from any place that has the repository checked out. To ensure that rsync is consistent and idempotent from the various places, I need to ensure that the time stamps and permissions of everything are in a known state. I already have a script that sets the timestamps of files based on when they were committed to git. I also have a script that sets the permissions on all files and directories to a known state. The only portion that I'm struggling with is bubbling time stamps from the files up to parent directories. I would like one line or short script that I can run from the command line to set directory timestamps based on the timestamps of their contents.