Guides

Business days are Monday–Friday; counting is exclusive (today is day 0) and skips weekends, while stricter versions also skip public holidays. '5 business days' usually means a full work week, landing one calendar week later.

A calendar year is 52 weeks and 1 day (2 days in a leap year), i.e. about 52.18 weeks on average. Under ISO week numbering most years have 52 weeks but some have 53, which affects weekly pay schedules and planning.

Net-30 and 'within X days' are counted exclusively from the start date (that day is day 0). Check whether the terms mean calendar or business days, and how weekends and holidays are handled, because those choices move the real due date.

Exclusive counting ignores the start day (today = 0) and suits countdowns; inclusive counting counts both endpoints and suits durations like rentals and billing. The two differ by exactly one day.

A day count depends on whose calendar day it is. Correct date math counts whole calendar days midnight-to-midnight in your local time zone — not in a server's time zone — which is why two countdowns can legitimately differ by a day.