For the official position on these, please see http://greenwichmeantime.com/info/noon.htm. Note the following, from that site, which contradicts the position stated by Joe Reid: Every day starts precisely at midnight and AM starts immediately after that point in time e.g. 00:00:01 AM (see also leap seconds) The following site agrees with my initial point in USMA 14642 (as also does the above site): http://www.boulder.nist.gov/timefreq/general/misc.htm Note the following sentence at that site: ... either 12 a.m. or 12 p.m. could work as a designation for midnight, but both would be ambiguous as to the date intended. At http://www.i5ive.com/article.cfm/english_grammar_style/64606, you'll find the following very lucid statement: "12 noon? 12 midnight? There is no "12 noon," just as there is no "12 midnight." It's just "noon" or "midnight." Don't even attempt "12 a.m." or "12 p.m." A.m. begins immediately after midnight, and p.m. begins immediately after noon. So 12 a.m. and 12 p.m. do not really exist." Stanford University very unambiguously (although redundantly) uses 12:00 noon and 12:00 midnight (although 24-hour clock would make more sense). See http://acomp.stanford.edu/acpubs/Docs/PublicClusters/pubclus.html. Another interesting site is: http://www.pubsprint.colostate.edu/resources/times.html Bill Potts, CMS Roseville, CA http://metric1.org [SI Navigator]
