On Do not use on before a date or day of the week when its absence would not lead to confusion, except at the beginning of a sentence: The meeting will be held Monday. He will be inaugurated Jan. 20. On Sept. 3, the committee will meet to discuss the issue.

Use on to avoid an awkward juxtaposition of a date and a proper name: John met Mary on Monday. He told Reagan on Thursday that the bill was doomed.

Use on also to avoid any suggestion that a date is the object of a transitive verb: The House killed on Tuesday a bid to raise taxes. The Senate postponed on Wednesday its consideration of a bill to reduce import duties.

The rule: Don’t use on before a day or date.

The exception: To avoid confusion with a proper name or to ensure it does not appear the actor in the sentence is doing something to the day.