How it is worked out
days remaining = target date − today
Why it is done this way
A countdown is a subtraction between two dates, but the useful part is the breakdown. Three hundred days means little; nine months and three weeks means something. Both are the same interval described at different resolutions.
Step by step
- Take today's date
- Count the calendar days to the target
- Break the result into years, months and days for the readable version
- Take out the weekends for the working-day count
What is worth knowing
The working-day figure is the one that matters when the countdown is to a delivery, a deadline or a launch, because that is the time you actually have to work in. Two details worth knowing: the count is in whole days from midnight, so a target later today shows as zero rather than as hours, and it uses calendar arithmetic rather than time zones, which means it does not shift depending on where you are. For a past date, the calculator says how long ago it was instead.