Day Counter — Days Between, Days Until
Days between two dates, the date N days from now, and anniversary counters with upcoming milestones — all in one place.
Runs in your browser — nothing is uploaded
How to use
Days between counts the days separating two dates — shown both as the plain difference and as an inclusive count (both ends included), which is what ticket windows and medication schedules usually mean.
Date after N days converts "90 days after release" or "30 days left" into an actual calendar date with its weekday.
Anniversary counter tells you what day you're on today, and lists the dates of upcoming milestones — day 100, day 1000, yearly anniversaries — so you can plan ahead.
"Day N" vs "N days later" — the off-by-one trap
Calendar subtraction says Jan 1 → Jan 3 is 2 days, but anniversary culture counts the first day as day 1, making Jan 3 "day 3". In other words, day N = (N−1) days later. The anniversary mode defaults to the day-1 convention; untick the box for elapsed-days counting (start day = day 0).
Notes
- Leap years are handled automatically.
- For Feb 29 anniversaries, non-leap years roll the date to Mar 1 (following the browser's calendar rules).
- Need business days (skipping weekends and Japanese holidays)? Use the business days calculator.