Can I check the day I was born?

Yes — pick your birth date and the tool tells you which weekday it was. It works for any past or future date your browser can represent.

What is the ISO weekday number?

ISO 8601 numbers the weekdays Monday=1 through Sunday=7. The tool shows this alongside the named day so you can use it in code or spreadsheets.

Is my date uploaded anywhere?

No — the weekday is computed entirely in your browser and nothing is ever uploaded.

Day of the Week Finder

What day of the week was — or will be — any date.

Day of the week finder

Find out which day of the week any date falls on — past or future. Pick a date and the tool shows the named weekday in large type, plus the ISO weekday number (Monday=1 … Sunday=7) and whether the date is a weekend.

Everything runs entirely in your browser — nothing is uploaded.