Guides
Last updated: October 28, 2026
These pages explain the same rule as the Days Since counter: a calendar date is local midnight, and a day is 24 hours of elapsed time. They are worked examples, not a certificate that an anniversary, a habit, or a deadline has been met.
The homepage opens on a sample, New Year’s Day 2026 (January 1). The calendar span from that date to October 28, 2026 is 300 days. The counter matches 300 days and 0 hours at local midnight on October 28 only when the device’s offset did not change in between. In a U.S. time zone that moved clocks forward on March 8, 2026, that midnight reads 299 days and 23 hours. Several guides use the same pair of dates so you can retype it. A whole number of days between two dates is a Gregorian date difference. Hours appear when the guide is talking about the clock.
The guides
- Counting anniversary days — why a 7th anniversary is not the same figure as the day count, with June 14, 2019 to June 14, 2026 as 2,557 days.
- Sobriety and habit day counts — using the counter as personal tracking. Milestones are arithmetic. This is not medical advice.
- How calendar days are counted — elapsed time versus inclusive dates, and why January 1 to October 28, 2026 is a 300-day calendar span.
- Time zones and daylight saving — local midnight, share links with no zone, and why a 23-hour civil day changes the count.
- Leap years and day counts — the Gregorian rule, February 29, and why one year is 365 days or 366.
- Milestone dates — 100 days, 365 days, and 1,000 days, and the calendar date when the counter reaches them.
What the counter will and will not do
It will recompute when you change the date. It will label the result with an optional event name. It will copy a link that contains the date and that name. It will remember the last date you calculated in this browser’s local storage.
It will not count a future date upward; a future date stays at zero. It will not turn the total into years and months. It will not skip weekends, and it will not know the hour the event happened, because the date is always midnight. It will not notify you when day 100 arrives. If your own calendar and the page disagree, the usual reasons are on the about page: you counted the start date as day 1, your device is in another time zone, or a daylight-saving change sits inside the span. Write to contact@days-since.app if a guide and the calculator disagree with each other.
What these pages will not claim
They will not call a holiday list an official federal calendar. They will not tell you that a sobriety count is treatment, or that a round number of days is a clinical threshold. They will not convert a legal deadline into advice. The age of a count is whatever date you typed. If a sentence here is wrong, email contact@days-since.app with the page and the sentence. The contact page says what to include.