The trouble is that AM & PM can both ONLY mean midnight ~~ ante meridiem = before noon & post-meridiem = after noon; & if you work it out, 12 hours after noon or 12 hours before noon are both midnight. That is why timetables which give 12 am & 12 pm are untrustworthy ~~ a lunchtime invitation for "12 pm" has a connotation obvious to the unthinking sender, who would however presumably be much put out if the invitee arrived at precisely midnight, when he was in actual fact invited for! So the terms 12 am & 12 pm should both be avoided, 'noon' & 'midnight' being substituted.

Unfortunately, this begs Bruce's cogent question, and leaves us no forrarder in answering it.

Still ~~ HNY to any who has stayed with me this far ~~ at 0712 GMT in the UK.

~M~