I was recently given a deadline of 12pm, which is meaningless by definition. The abbreviations ‘am’ and ‘pm’ mean ante meridiem and post meridiem – before and after noon. 12 noon cannot be either before or after noon because it is noon. 12 midnight is both before and after noon, and by the same margin.
The culprit had at least three alternative ways to express him/herself:
- Words: ‘noon’ or ‘midnight’.
- 24-hour clock: ‘1200’ or ‘2400’.
- One-minute-off: ’11:59am’ or ’11:59pm’.
Airlines usually combine the last two of these for midnight departures or arrivals, to avoid any confusion about the date.
Don’t mind me: I’m just letting off steam. I’m sure none of my readers would be guilty of such an elementary mistake.
StroppyGit 
A pedantic realist might argue that the moment of noon-ness is infinitely small and therefore non-existent; and by the time the eye has detected and the brain processed the physical evidence of noon-ness that moment has passed.
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It is much worse that you depict!
11.59am
11:59:59am
then tick over anotehr second
12:00:00am?
No. It is 12:00:00pm
How so?
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