This is probably my fault; it turns out I've been incorrectly spelling it antemeridian for ages! Antemeridian is an adjective meaning "of or relating to mornin

This is probably my fault; it turns out I've been incorrectly spelling it antemeridian for ages! Antemeridian is an adjective meaning "of or relating to morning", and antimeridian is indeed the correct word. Thanks, Rob!