Subtracting days from a date answers the backwards question: if something must be finished on a given day, when does it have to start? Notice periods, cancellation windows, booking cut-offs, print deadlines and the countdown to an event all work this way, and the arithmetic is where errors are expensive rather than merely untidy.
The convention matches the forward version: subtracting one day from a Monday gives the Sunday, so the count is of days between rather than of days in a list. A rule that says notice must be given not less than 28 days before a date sets the last permissible day at the result shown here — and if the rule says clear days, the margin is one day tighter still.
Landing on a weekend or a bank holiday is the situation to watch. Nothing in a plain day count moves the result off a Sunday or off Boxing Day, but the office that has to receive the notice will be shut. Because the British bank holiday list differs between England and Wales, Scotland and Northern Ireland, a date that is fine for a Cardiff deadline may be a closed day for a Belfast one. The calculator shows the weekday and flags a bank holiday where the result hits one, so the clash is visible before it becomes a problem.
Cookie policy