What Day of the Year Is It?

For quick planning, progress tracking, or date math, a single number is often all you need. This page reads your device clock, determines whether it’s a leap year, and computes the exact day of the year—also called the day number or ordinal date. The large figure above is that day count; the smaller line underneath shows the corresponding ISO week. Because the calculation uses your current time zone, it matches what your calendar shows right now, wherever you are.

What does “day of the year” mean? We count days from January 1 (Day 1) up to December 31 (Day 365, or Day 366 in a leap year). If today is Day 302, that means 301 days have already passed this year. It’s a compact way to track progress through the year, estimate deadlines, and compare dates across different months without mental gymnastics.

How do we calculate it? The script takes the current date from your device, normalizes for daylight-saving offsets, and subtracts January 1 to get a day difference. That difference becomes the ordinal number you see in big text. Nothing is sent to a server; it all happens in your browser so it’s private, fast, and resilient even if you’re offline.

ISO week numbers at a glance. The small line labeled “Week NN” follows the ISO week-date system: weeks start on Monday, and Week 01 is the week that contains January 4. Most years have 52 ISO weeks, but a few have 53 depending on how the days line up. This convention is used widely in Europe and in engineering schedules because it avoids ambiguity.

Why is this useful? Day numbers shine in operations, finance close calendars, project burn-down charts, academic terms, and content planning. They’re also handy for spreadsheets and simple formulas. For example, in Excel or Google Sheets you can compute the day of the year with =A1-DATE(YEAR(A1),1,0) (where A1 is a date). For the ISO week number, many spreadsheet apps provide ISOWEEKNUM(). Using these together lets you filter by week or compute “days remaining in the year” at a glance.

Leap years and edge cases. Leap years add February 29, so the maximum day number becomes 366. The page automatically accounts for that using the standard Gregorian leap-year rules (divisible by 4, but centuries must also be divisible by 400). If something looks off, it’s almost always a device clock or time-zone setting—turning on automatic date & time fixes nearly every issue.

Related tools. If you need a human-readable string like “Wednesday, October 29, 2025,” jump to our today’s date page. If you’re coordinating sprints, releases, or academic weeks, our week of the year page explains ISO week math and shows the current week with examples. Together, these tools cover both natural-language dates and machine-friendly formats (YYYY-MM-DD, ISO weeks, and ordinal dates) so you can copy exactly what you need.

Tips for documentation and teams. When writing procedures or tickets, referencing an ISO week or a day number can be clearer than a regional date like 10/12/2025 (which might mean October 12 or December 10 depending on country). Use the day number for progress (“Day 200: 54% of the year complete”) and the ISO week for scheduling (“deploy in Week 44”). If you keep both in your vocabulary, your docs will stay consistent across time zones and locales.