About daysuntil.us
Updated November 9, 2026
daysuntil.us is a set of free date calculators and countdowns to US holidays. Each page gives one number first, then shows how it was counted, so you can check it against your own calendar. The tools are the days calculator, days from today, business days, Christmas countdown and birthday countdown.
How we count
One counting rule is used on every page, with the same wording:
- All date maths uses UTC-midnight timestamps built from the year, month and day, so daylight saving time cannot shift a day.
- Days between two dates = (later date − earlier date) ÷ 86,400,000 milliseconds, always a whole number.
- Weekdays are the Monday-to-Friday dates in the counted span. The start date is not counted and the end date is.
In plain terms, we count calendar days by date. The start date is not counted and the end date is, so today to tomorrow is 1 day. The home page calculator has an option to count both ends, which adds one day, and it says so next to the answer.
Countdowns and timers
A live timer counts complete 24-hour days to midnight at the start of the event in your time zone, so it can show one day fewer than the date count. Where both appear on a page, the page says so.
Years, months and days
The split adds whole months to the earlier date, clamping to the last day of a shorter month, then counts the remaining days. The method is explained on the home page.
How pages stay accurate
Numbers printed in the page text, such as the days left to an event, are calculated when the site is built, and the site is rebuilt every day. The calculators and timers then use the date on your device, so a result can differ by a day from the printed text near midnight.
Every calculator has automated test cases that cover normal inputs, boundaries such as leap days and month ends, and invalid dates, and the build checks the date engine against known results before it publishes.
Sources and credits
The site does not use any downloaded third-party dataset. The one table of rules it relies on is the list of US federal holidays and their observed days, taken from 5 U.S.C. 6103 and the US Office of Personnel Management federal holidays page. Dates are computed from those rules rather than copied.
Thanksgiving is the fourth Thursday of November under the same statute.
Contact
To report a wrong date or a bug, see the contact page. Our privacy policy and terms of use explain how the site works with your data and how to use the results.