The last modification time of a directory (think like phone directory, not folder) is the time it was last modified, like when an entry was removed, added or edited in that directory.
To find out the newest regular file recursively in it, you would need to read the contents of that directory and every directory within and for each file, check the file's modification time. That's a costly thing to do, I wouldn't expect any file manager application to do it.
You could however script it.
With the GNU implementations of find and sort (and any Bourne-like shell), you could do:
TZ=UTC0 find . -mindepth 2 -type f -printf '%TFZ%TT/%P\0' |
LC_ALL=C sort -zt/ -k2,2 -k1,1r |
LC_ALL=C sort -t/ -zmsuk2,2 |
LC_ALL=C sort -z |
tr '\0' '\n'
Which would give something like:
2020-02-08Z19:17:22.3588966190/Scripts/.distfiles
2020-02-09Z09:25:37.5336986350/StartupFiles/zshrc
2020-07-26Z20:33:17.7263164070/Misc/vcs_info-examples
2020-07-26Z20:33:17.7463157170/Util/ztst-syntax.vim
2020-08-22Z18:06:17.9773156630/Functions/VCS_Info
2020-08-30Z11:11:00.5701005930/autom4te.cache/requests
2020-08-30Z11:11:31.5245491550/Config/defs.mk
2020-08-30Z11:11:31.6085449480/Etc/Makefile
2020-08-30Z11:12:10.9305773600/INSTALL.d/share/zsh/5.8.0.2-dev/help
2020-10-22Z05:17:15.3808945480/Completion/Base/Utility
2020-10-22Z05:17:15.3928938520/Doc/Zsh/zle.yo
2020-10-22Z05:17:15.3968936190/Src/zsh.h
2020-10-22Z05:17:15.3968936190/Test/D02glob.ztst
2020-10-22Z05:17:15.4168924590/.git/logs/refs/heads/master
That is, giving the newest regular file in each directory with its timestamp. Directories without regular files in them are not shown.
To only see the list of directories, insert a cut -zd/ -f2 | before the tr command.
For a prettier output like in the zsh approach, you could replace the tr command with:
LC_ALL=C gawk -v RS='\0' -F / '{
dir = $2; mtime = $1
sub("[^/]*/[^/]*/", "")
printf "%-20s %s (%s)\n", dir, mtime, $0}'
While we're at using gawk, we could also tell find to print the timestamp as a fractional Unix epoch time and gawk reformat it in local time:
find . -mindepth 2 -type f -printf '%T@/%P\0' |
LC_ALL=C sort -zt/ -k2,2 -k1,1rn |
LC_ALL=C sort -t/ -zmsuk2,2 |
LC_ALL=C sort -zn |
LC_ALL=C gawk -v RS='\0' -F / '{
dir = $2; split($1, mtime, ".")
sub("[^/]*/", "")
printf "%-20s %s (%s)\n", dir, strftime("%FT%T." mtime[2] "%z", mtime[1]), $0}'
Which would give an output like:
cross-build 2019-12-02T13:48:33.0505299150+0000 (cross-build/x86-beos.cache)
m4 2019-12-02T13:48:33.4615093990+0000 (m4/xsize.m4)
autom4te.cache 2019-12-02T13:50:48.8897482560+0000 (autom4te.cache/requests)
CWRU 2020-08-09T17:17:21.4712835520+0100 (CWRU/CWRU.chlog)
include 2020-08-09T17:17:21.5872807740+0100 (include/posixtime.h)
tests 2020-08-09T17:17:21.8392747400+0100 (tests/type.right)
.git 2020-08-09T17:17:21.8472745490+0100 (.git/index)
doc 2020-08-09T17:35:35.1638603570+0100 (doc/Makefile)
po 2020-08-09T17:35:35.3758514290+0100 (po/Makefile)
support 2020-08-09T17:35:36.7037954930+0100 (support/man2html)
lib 2020-08-09T17:35:42.3755564970+0100 (lib/readline/libhistory.a)
builtins 2020-08-09T17:35:42.5035511020+0100 (builtins/libbuiltins.a)
examples 2020-08-09T17:35:47.1513551370+0100 (examples/loadables/cut)
INSTALL.d 2020-08-09T17:35:47.3993446790+0100 (INSTALL.d/lib/bash/cut)
%TM.%Tmwould be the month. See also%TR(same as%TH:%TM). Also note that if you don't use%Tz, you get an ambiguous output for some times of the year in timezones that do dst. You can also combine the twotrs totr '\0/' '\n\t'ncdu. Run with-e, then typemthenMto see the results. (Sadly, it's export mode does not place these "derived" timestamps in the file; I just checked, hoping it would! So you can only see those timestamps within thencduprogram)