POSIX says: A target shall be considered up-to-date... if it has already been made up-to-date by the current invocation of make (regardless of the target's existence or age). If the target does not exist after the target has been successfully made up-to-date, the target shall be treated as being newer than any target for which it is a prerequisite. Previously 'make' assumed that if a rule had succeeded the modification time of the target would be the current time. This isn't necessarily the case. Instead: - If the file exists use the modification time of the file as the the time of the target. - If it doesn't exist use the current time, which should be more recent than the time of any file for which it's a prerequisite. Adds 16 bytes. (GitHub issue #410)