What is the day of year?

The day of year (or ordinal day) numbers every day from 1 on 1 January up to 365, or 366 in a leap year, on 31 December. It is sometimes loosely called the Julian day in agriculture, manufacturing and IT.

How is the ISO week number defined?

ISO 8601 weeks start on Monday, and week 1 is the week containing the year's first Thursday. This tool computes the ISO week number for the selected date using that standard.

Is my date uploaded anywhere?

No. The calculation runs entirely in your browser using local date arithmetic — nothing is sent to a server.

Day of Year Calculator

Find the ordinal day number and ISO week for any date.

What day of the year is it?

The day of year (or ordinal day) numbers each day from 1 on 1 January to 365 — or 366 in a leap year — on 31 December. It is widely used in manufacturing date codes, agriculture, logistics and IT systems, where it is sometimes loosely called the “Julian day”.

Pick any date and this calculator returns its ordinal day number, how many days remain in the year, and the ISO 8601 week number — all computed locally in your browser.