When is midnight?

Is “midnight Wednesday” between Tuesday and Wednesday or between Wednesday and Thursday? First thought is the latter, but if midnight is 12:00 AM, than it’s the former, right?
Isn’t 12:00 AM Wednesday midnight? Is it Tuesday’s “midnight”? Shouldn’t 12:00 AM belong to the same day as 12:01 AM?
Is New Year’s Eve midnight Jan. 1st at 12:00 AM? Then “December 31st’s midnight” is between December 31st and Jan. 1st, eh? So what is 12:00 AM December 31st? – midnight Dec. 30th?
When do laws effective at midnight take effect? (i.e what day?)

Midnight is 00:00. This time is the beginning of a new day, not the end of a previous one. The previous day ends at 23:59

So Wednesday at mignight should be the beginning of Wednesday at 00:00, but since so many people get confused by this, you have to ask if they mean the end of Tuesday or not…

If you go read the fine print, you’ll find that most laws (and insurance policies, etc.) do not start at midnight; they start at 12:01 a.m. I know many of you disagree, because you have your own convention. However, there is not such time as 12:00 pm (it’s either 12 noon or 12 midnight). And midnight is the instant between two days so “Midnight, January 21st” does not exist. The 24 hour clock removes this ambiguity because 24:00 on Monday (which is also 00:00 on Tuesday) is not confusing.

The 12:01 am clause is to assure that whoever signs a contract understands exactly what calendar day it is to be enacted. That is, 12:01 am Tuesday is definate; midnight Tuesday can be taken two different ways.

Cecil discusses midnight in This Article