> If we decide to change the format this regex will be forgotten as is. Personally I would define a string in logging.h, e.g. LOGGING_TIMESTAMP_REGEX. A test that it actually matches would be an extra bonus... ;-)

Good idea!

Note that the timezone is not matched; I avoided it specifically because of Windows. It doesn't need to match though, because I don't use the regex to remove the timestamp, I only use it to have reasonable confidence that the line starts with one. The actual removal happens by looking for the ": " delimiter. So neither Windows nor Daylight Saving should be a problem.