dired-sort-by-date-regexp

dired-sort-by-date-regexp is a variable defined in `dired.el'.
Its value is

"\\(\\`\\| \\)-[^- ]*t[^ SXU]*\\(\\(\\`\\| +\\)\\(--[^ ]+\\|-[^- tSXU]+\\)\\)* *$"

Documentation:
Regexp recognized by Dired to set `by date' mode.