Apparently, although both “at the 100th anniversary” and “on the 100th anniversary” are used commonly, using the preposition on is more common according to Google search results. I’d like to ask that whether using at is a grammar error or whether there are special structures in which it is preferred to be used.

  • As a general rule: use at for a PRECISE TIME, in for MONTHS, YEARS, CENTURIES and LONG PERIODS on for DAYS and DATES : englishclub.com/grammar/prepositions-at-in-on-time.htm
    – user5267
    Commented Aug 21, 2016 at 7:54
  • @Josh61 dude I know how to use prepositions in general.The link you gave does not help really. Thank you though.
    – Mrt
    Commented Aug 21, 2016 at 8:22
  • So what are you looking for? If you know that "on" is the correct preposition what's the point of asking? If "at" is used referring to an anniversary it most likely refers to the place/party, not the date.
    – user5267
    Commented Aug 21, 2016 at 8:23
  • 2
    Usage of at vs on is by far less common, and as you can see at is used to refer to the place/party of the anniversary not to its date. There may be non standard usages also. books.google.com/ngrams/… - the sentence you have linked above is quite clear: at his anniversary concert.
    – user5267
    Commented Aug 21, 2016 at 8:35

2 Answers 2


I suggest you to use "on" in the sentence "... on the 100th anniversary" as it implies that the author is talking about a particular occasion - a specific day. On is used with days, parts of the days, dates, particular occasions, anniversaries and festivals.

I use the links hereinbelow as references:

on - Merriam-Webster: 3 — used as a function word to indicate a time frame during which something takes place or an instant, action, or occurrence when something begins or is done

on - WordReference: 20 - at the time or occasion of: You have to pay cash on delivery (= at the time delivery is made).

I hope this answers your question well.


At the 100th anniversary impiles that the 100th anniversary is an event, likely one that people can attend. Since it happens at a point in time it can be used that way as well.

I'm trying to get this gift so I can give it to her at her 100th anniversary. (You might be taking her out to dinner, which you are considering an event, and giving her the gift then. Or you might be throwing her a party and will give it to her at the party.)

I'm trying to get this gift so I can give it to her on her 100th anniversary. (You are just saying you're going to give it to her on the day of her 100th anniversary, but no implication about a party or event.)

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