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----- Original Message -----
From: "Bill Potts" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[EMAIL PROTECTED]>
Sent: Thursday, 2004-01-01 15:18
Subject: [USMA:28071] RE: Calendar, date and time

Ah, I misunderstood you.

Let's start again on that. I assumed you knew noon was at 12:00 (as expressed in 24 hour time).

Whether, in the am/pm scheme, noon is 12 am or 12 pm is an issue with me, too. I've always regarded it as more logical to use 12 am, with pm occurring (at 12:00:01) an instant later.
 
You are half correct.  Noon, exactly 12:00:00, is neither am or pm.  AM means ante meridian (before noon) and PM means post meridian (after noon).  Since noon is the meridian, it is neither am nor pm.  
 
12 pm makes sense for midnight, as that time is exactly 12 hours post meridiem (i.e., past the sun's [nominal] highest point). However, common practice is, illogically, the reverse of that.
 
Common practice is correct if you mean midnight to be the start of the day so that midnight then appears 12 h before the meridian, thus AM.   I explained this in another posting, so I won't repeat it here.  Just read my explanation.


For this reason, if I find myself forced to use 12-hour time, I refer to the two 12s as 12 noon and 12 mid (or 12 midnight), avoiding the am/pm issue altogether.
 
I just stick with the terms noon and midnight.  I save myself the bother of adding the 12:00 part as that should be self understood.


Bill Potts, CMS
Roseville, CA
http://metric1.org [SI Navigator]
 
Euric


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