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What time is 12am?

What time is 12am? What time is 12pm? An entertaining discussion on the Chiswick W4 site on what time is 12 am? Local Tom O’Keefe informs us:

I received a PCN [Parking Fine Ticket]today for parking at 14:22 in a bay near Hoxton square (Hackney) that showed parking to be restricted between 8.30am and 12.00am. I assumed that 8.30am to 12.00am meant restrictions for the 3 and a half hours following 8.30am, but since I have received a PCN can only assume 12.00am means 12 midnight.

The truth of the matter was revealed quickly when local councillor Chris Calvi-Freeman (who happens to be our representative for all things traffic and roads), brought in not the authority of traffic law, but that of his dad:

I can recall my old dad, a master mariner, telling me that there was no such time as 12.00am or 12.00pm – they were 12 noon or 12 midnight.

And he’s right: there’s no such time as either 12 am or 12 pm. As NIST, the US’s National Institute of Standards and Technology explains:

…12 a.m. and 12 p.m. are wrong and should not be used.

To illustrate this, consider that “a.m” and “p.m.” are abbreviations for “ante meridiem” and “post meridiem.” They mean “before noon” and “after noon,” respectively. Noon is neither before or after noon; it is simply noon. Therefore, neither the “a.m.” nor “p.m.” designation is correct. On the other hand, midnight is both 12 hours before noon and 12 hours after noon. Therefore, 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.

So now you know and if you get an invite for a meeting at 12 am, just don’t turn up, as it clearly is going to be a waste of time! Whether Tom’s parking ticket appeal will work and he is let off his parking fine, is still a moot point…

Update: Hackney Council saw sense and removed the PCN. Wonder if they let the next person off?

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