org-plain-time-extension-regexp

org-plain-time-extension-regexp is a variable defined in `org.el'.
Its value is

"\\(\\<[012]?[0-9]\\(\\(:\\([0-5][0-9]\\([AaPp][Mm]\\)?\\)\\)\\|\\([AaPp][Mm]\\)\\)\\>\\)\\+\\([0-9]+\\)\\(:\\([0-5][0-9]\\)\\)?"

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

Documentation:
Regular expression to match a time range like 13:30+2:10 = 13:30-15:40.
Examples: 11:45 or 8am-13:15 or 2:45-2:45pm. After a match, the following
groups carry important information:
0 the full match
7 hours of duration
9 minutes of duration