I am aware that one uses "on" for dates and "at" for times.

However, when there is both -- in my case in a form or table in a web application, but it could just as well be a printed application form or something similar -- which preposition should I use?

Here's a snippet from my case:

screenshot with table heading "Last Changed At"

I suppose I could just change it to "Last Change" or "Last Changed", but even so I do wonder if "at" is wrong here.

I have seen Preposition at: This invoice was issued at March 21, 2018 and Using prepositions with date and time but those don't really answer my question.

  • 4
    It's OK in an app, to disregard strict rules like this, however, I'd prefer just 'Last changed'. Commented Jan 31, 2023 at 12:27
  • 'Modified' is a commonly used and understood column header in situations such as yours and avoids the necessity to use a preposition.
    – KnotWright
    Commented Jan 31, 2023 at 20:20

1 Answer 1


At for times. On for dates.

My appointment is at 3pm.

My appointment is on the 10th of February.

My appointment is at 3pm on the 10th.

But in your screen shot example, it's a heading. So that immediately changes the rules. By definition the heading will be a shortened form of the full sentence, or it will follow its own grammar. "Last changed at..." and last changed on..." will both be correct, because you're effectively using an unfinished sentence as your header, and it depends entirely on how you would finish that sentence.

If you want the grammar of the heading to be correct, I would consider changing the form from verb to noun: something like "Last change" or "Last revision". Those options would also depend on the contents of other columns and their related heading styles.

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