Add option -Z to syslogd(8) to use ISO 8601 timestamps
When doing global remote logging and archiving, it is inconvenient
that the syslog timestamp does not contain the year and the timezone,
but has local time with daylight saving time.
Now with -Z syslogd(8) switches to RFC 5424 ISO format for timestamps.
Then all logging is also done in UTC. Default is to keep local
time and BSD syslog RFC 3164 format.
Syslog RFC 5424 says you should add 1 to 6 digits with fractions
of a second to each syslog timestamp. As we do not measure the
time in syslog(3), use only 3 digits with millisecond precision.
Code taken from OpenBSD, where it was originally developed by bluhm:
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/syslogd/syslogd.c.diff?r1=1.215&r2=1.216&f=h
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/syslogd/syslogd.c.diff?r1=1.216&r2=1.217&f=h
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/syslogd/syslogd.8.diff?r1=1.50&r2=1.51&f=h
IETF reference standards (RFC) for syslog:
https://tools.ietf.org/html/rfc3164#section-4.1.2
https://tools.ietf.org/html/rfc5424#section-6.2.3