Lifehacker is running the following “tip” to convert a time specified in 24-hour notation to one in 12-hour notation:
Subtract 10 then 2 to get the 12 hour clock time.
This is not so much a “tip” as a restatement of the definition. 24-hour times between 13:00 and 23:59 correspond to 12-hour times that are … yes, 12 less in the hours place. When challenged on the triviality of this algorithm, the author, Gina Trapani, responded:
I think because 10 and 2 are easier to subtract than 12 or 6.
The comments thread has been filling with well-deserved ridicule, which, to her credit, Trapani has been taking with good humor. Still, the only difference I can see between this “handy” technique and the good old-fashioned method called “subtracting 12” is that the old-fashioned method first subtracts 2 and then subtracts 10, instead of vice-versa. Apparently, the target Lifehacker audience consists of people who can hold in their memory numbers up through and including 14 but not numbers as exorbitantly large as 22.