Days ago calculator

Counting back a fixed number of days is unambiguous in a way that counting back months is not: thirty days before 31 March is 1 March, and one month before 31 March is 28 February, and those are different dates for a good reason. If a deadline is defined in days, count days; if it is defined in months, count calendar months and accept that the end-of-month cases clamp. The distinction shows up in contracts constantly, and the phrases "within 30 days" and "within one month" are genuinely different obligations. The weekday is the fastest check that you have the sign and the number right, and it moves predictably: going back seven or fourteen days leaves the weekday alone, back thirty moves it two days earlier, and back ninety moves it one day later, because ninety is thirteen weeks less a day. Nothing here is affected by a clock change, incidentally. The arithmetic works in whole calendar dates, so a "day" is a date rather than 86,400 seconds and daylight saving never enters into it.