The day of year works like this: it converts dates to their ordinal day number and days-remaining count within the year. Everything happens on your device - the input never leaves your tab unless the tool clearly states it performs a server-side lookup.
How to use the Day of Year
Enter the date, time or duration you start from.
Add the operation's parameters.
Read the result, which updates live.
Copy values you need elsewhere.
Features
Find day number of year from any date
Instant result, no page reload
Works in any modern browser, desktop or mobile
Free with no signup
Common mistakes to avoid
Swapping day and month when entering dates
Examples
Input
Result
20 Sep 2026
Day 263 of 365 · 102 days remaining
Best used for
Getting a reliable answer for day of year without installing an app
One-off tasks done in under a minute from any device
Checking results before committing them to something important
Working on a phone where desktop software is unavailable
Privacy
Date math runs locally in your browser.
Frequently asked questions
How do leap years change the count?
Dates after 28 Feb shift by one: 20 Sep is day 263 in common years, 264 in leap years.
What is the day-of-year number used for?
Project timelines and seasonal comparisons - "day 256" is unambiguous where "around mid-September" is not, and the companion days-remaining count supports countdown planning.
Does the count include the date itself?
Yes - January 1 is day 1, and December 31 is day 365 or 366 depending on the leap year, which the tool states explicitly.