March 24.

Do you adjust the dates depending on whether a month is 30 days or 31?

I would answer March 24, but I would not usually say something is in one month and mean the same date in the next month. I usually think in terms of weeks or same day in the next month, like the third Thursday of a month.

At this point it would be March 24th but, let us adjust the calendar so that each month has twenty-eight days and take the remainder as a holiday at the end of the year and every four years we get an extra day off.

We would need a name for the thirteenth month but maybe we can hold a contest.

Count four weeks.

Usually, when people say “a month after” they just mean the same date, the next month. Don’t overthink it.

It depends on the reason why you were referring to “one month later”. If you mean on the 24th of each month then the number of days will vary by up to 3 (28 days, 30 days or 31 days in the month). If you mean the last Thursday of the month then it will be 4 or 5 weeks later, depending when that Thursday falls. Sometimes people say a month when they mean 4 weeks. That would be fixed but you would find that the date would change significantly and that there are 13×4 week intervals in a year.

Why were you asking?

@Stinley I am asking because I’m quitting something I did on February 24th and I would like to celebrate my months of being “clean”.

I would say that you celebrate on 24th of the month. I.e. 24th march = 1 month since I gave up xxx