1. answered Oct 5, 2013 at 21:12. Tyler James Young. 11.4k 1 35 57. Add a comment. 0. Another easier way to remember is: in a period, on a day, at a time. while year is a long period, so it is always "in" a year; a time like 7 o'clock is very specific, thus we use "at" all the time. hope this help. More @Wikipedia
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