December 16, 2007

At that second, on that day, in that year

Talking of the interaction of syntactic preposition choice and meaning, as Mark just was, the Movable Type software used by Language Log automatically puts at the bottom of each post a little message like this:

Posted by Mark Liberman at December 16, 2007 08:15 AM

But of course that is ungrammatical. We don't say at December 16, ever. In fact the principles of preposition choice for specifying temporal locations (as opposed to durations extending from now into the future, like in a few seconds) seem to be as follows:

at for seconds (at that very second)
at for minutes (at 15 minutes past the hour)
at for hours (at eight in the morning)
on for days (on December 16)
in for weeks (in the third week of December)
in for months (in December)
in for years (in 2007)

But why? Why is it at for short periods of time recorded on a clock face, on for medium ones punctuated by the cycle of sunrise and sunset, and in for longer ones recorded in the calendar? One day I might set that as an essay question in a course on grammar and meaning. I have no idea what the right thing to say about it would be, though. I suppose my email account will be deluged with messages from people who want to explain it to me. Please be tolerant with me if it proves simply impossible for me to respond to them all. I have no staff for this sort of thing, you know; and I have are many other duties, from writing letters of recommendation (sorry about the delay, Frank) to Christmas shopping. But thank you in advance for whatever you send.

[Update: Nicole Perrin tells me that accountants do say "at December 16"; fair enough. I'm talking about ordinary non-accountant usage. Jonathan Lundell points out that we actually don't have any way to talk about being located within a certain 60 minute period, as opposed to being located at an exact instant like at 8 a.m.; I think he's right. John Lawler has sent a brief but detail-packed essay about dimensionality and metaphoricity in uses of at and on and in, which I may post separately.]

Posted by Geoffrey K. Pullum at December 16, 2007 10:59 AM