Every countdown needs a convention, and this one uses the natural one: how many midnights stand between now and then. Tomorrow is 1 day away, today is 0, and yesterday flips the calculator into "days since" mode automatically.
Holidays that compute themselves
The preset chips don't store dates — they calculate the next occurrence live. Click Christmas on December 26 and you get next year's count, 364 days (365 across a leap year). Leap years are handled exactly, because the math runs on real calendar dates rather than 365-day approximations.
Working days: the deadline view
For deadlines, weekends don't count. The working-day figure counts Mondays through Fridays only — 30 calendar days typically contain just 21–22 of them, which is why deadlines always feel closer than the calendar suggests. Public holidays vary by country and aren't subtracted, so treat the number as an upper bound of true business days.
Days since: streaks and anniversaries
Pick a past date and the tool counts forward from it — days since a launch, a quit date, a wedding. For full calendar arithmetic in years, months and days, the age calculator and date calculator go deeper; for elapsed hours and minutes, use the time duration calculator.
Why weeks, not months
Months are slippery units — 28 to 31 days — so countdowns stick to exact days and weeks. 100 days is always 14 weeks and 2 days, whether it crosses February or July. If you need "3 months from today" resolved to a date, that's exactly what the date calculator does.
All math runs locally in your browser — works offline.