If you need to clean up a file system (especially your $HOME directory from some ancient dot-files), it may be useful to sort the top-level directories by the last modified time of any file inside them.
Here’s the command I came up with:
And here’s how the output looks like:
2007-07-30 .gkrellm2 2007-08-04 .gobby 2007-08-17 .imgseek 2007-08-25 .kderc 2007-09-12 .ftp_banner 2007-09-18 .BitchX ...
Thank you to numerous StackOverflow users from whose questions and answers I benefited; in particular the ones about printing mtime from find and sorting an AWK array.