org-stamp-time-of-day-regexp

org-stamp-time-of-day-regexp is a variable defined in `org.el'.
Its value is

"<\\([0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\} +\\sw+ +\\)\\([012][0-9]:[0-5][0-9]\\(-\\([012][0-9]:[0-5][0-9]\\)\\)?[^\n
>]*?\\)>\\(--?<\\1\\([012][0-9]:[0-5][0-9]\\)>\\)?"

• This variable may be risky if used as a file-local variable.

Documentation:
Regular expression to match a timestamp time or time range.
After a match, the following groups carry important information:
0 the full match
1 date plus weekday, for back referencing to make sure both times are on the same day
2 the first time, range or not
4 the second time, if it is a range.