I saw a man today wearing a t-shirt printed on the back with:
Don’t wait until midnight
Just as I was starting to make guesses about what was going to happen at midnight, he turned around and I saw the front:
No man knows the date or the hour
I know enough Bible to get that this is a reference to The Rapture:* Don’t think you can wait until the last minute to get yourself sorted out with God, because no one knows when he might show up and slaughter all the unrepentant masses.
But my first thought was that this is good advice for life generally: no one knows what you mean when you say midnight. If God announced that everyone should be packed and ready to go at midnight on April 18, at least half of his followers would miss the Rapture Train because they showed up at the end of April 18 instead of the beginning. That’s why lawyers don’t use midnight in contracts: they use 11:59pm or 12:01am (and if you’re listening, God, be sure to specify which time zone you’re referring to, too).
The Bible doesn’t actually cite midnight as the cause of the confusion, but we can interpret it that way:
But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father….Two men will be in the field; one will be taken and the other left. Two women will be grinding with a hand mill; one will be taken and the other left.
Therefore keep watch, because you do not know on what day your Lord will come. But understand this: If the owner of the house had known at what time of night the thief was coming, he would have kept watch and would not have let his house be broken into.
Clearly, one of those men and one of those women were confused about what midnight refers to. I don’t know what this house is all of a sudden, or why God’s return is being likened to a thief breaking into a house (isn’t his return supposed to be a good thing?), or why the Bible is telling us to keep watch when it is also telling us that there is no point in keeping watch because we cannot know when to keep watch, but “keep watch” obviously means “make sure your am/pm is set right on your watch and understand when midnight is.”
The advice from the United States Institute of Standards and Technology is slightly more straightforward :
Are noon and midnight referred to as 12 a.m. or 12 p.m.?
This is a tricky question because 12 a.m. and 12 p.m. are ambiguous and should not be used.
To illustrate this, consider that “a.m.” and “p.m.” are abbreviations for “ante meridiem” and “post meridiem,” which mean “before noon” and “after noon,” respectively. Since noon is neither before noon nor after noon, a designation of either a.m. or p.m. is incorrect. Also, midnight is both twelve hours before noon and twelve hours after noon.
It is fair to say, however, that the shortest measurable duration after noon should be designated as p.m. For example, it would be applicable for a digital clock changing from 11:59:59 a.m. to 12:00:00 to indicate p.m. as soon as it the 12:00 appears, and not delay the display of the p.m. by a minute, or even a second. The same is true for midnight, but there is an added issue of which day midnight refers to (see below).
Hours of operation for a business or other references to a block of time should also follow this designation rule.
For example, a business might be open on Saturdays from 8 a.m. to noon or weekends from 3:30 p.m. until midnight.
Is midnight the end of a day or the beginning of a day?
When someone refers to “midnight tonight” or “midnight last night” the reference of time is obvious. However, if a date/time is referred to as “at midnight on Friday, October 20th” the intention could be either midnight the beginning of the day or midnight at the end of the day.
To avoid ambiguity, specification of an event as occurring on a particular day at 11:59 p.m. or 12:01 a.m. is a good idea, especially legal documents such as contracts and insurance policies. Another option would be to use 24-hour clock, using the designation of 0000 to refer to midnight at the beginning of a given day (or date) and 2400 to designate the end of a given day (or date).