# Day of Year Calculator

> Find the ordinal day number, week number, quarter and how much of the year has elapsed.

The day of the year, or ordinal date, counts from 1 on 1 January to 365 or 366 on 31 December. This calculator also gives the ISO week number, the quarter, the Julian Day Number used in astronomy, the Unix timestamp, and the percentage of the year elapsed.

**URL:** https://convertto.tech/t/day-of-year-calculator
**Category:** Date & Time Tools (https://convertto.tech/c/date-time-tools)
**Privacy:** Runs entirely in the browser; no upload
**Cost:** Free, no sign-up
**Last updated:** 2026-08-01

## Key facts

- **Privacy:** Runs entirely in your browser — nothing is uploaded
- **Cost:** Free, unlimited, no sign-up

## How to use

1. Enter or paste your date.
2. The result appears immediately — copy or download it.

## FAQ

### What is an ISO week number?

A week numbering where week 1 is the one containing the year's first Thursday. It means early January can fall in week 52 of the previous year — which surprises people but keeps every week a full seven days.

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