In English, at least, it used to be that a document such as a letter would begin with a date indicating when it was written, and then for dates ±1 month from th

In English, at least, it used to be that a document such as a letter would begin with a date indicating when it was written, and then for dates ±1 month from that date would express relatively, like so: * "The 10th instant" / "10th inst." = tenth day of current month indicated in date of document * "The 10th ultimo" / "10th ult." = tenth day of month preceding the one indicated in date of document * "The 10th proximo" / "10th prox." = tenth day of month following the one indicated in date of document