Although the source for the fourth edition is not available, the man page for the ctime(3) library function is: https://minnie.tuhs.org/cgi-bin/utree.pl?file=V

Although the source for the fourth edition is not available, the man page for the ctime(3) library function is: https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/man/man3/ctime.3 https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/man/man3/ct... It confirms that the day of the month element was one based. This function is different in earlier editions: https://minnie.tuhs.org/cgi-bin/utree.pl?file=V3/man/man3/ctime.3 https://minnie.tuhs.org/cgi-bin/utree.pl?file=V3/man/man3/ct... https://minnie.tuhs.org/cgi-bin/utree.pl?file=V1/man/man3/ctime.3 https://minnie.tuhs.org/cgi-bin/utree.pl?file=V1/man/man3/ct...