Shows weekday, ISO week, day-of-year and more for a date.
Date Info takes any date you enter and shows its calendar details: the weekday, the day of the year, the ISO week number, the calendar quarter, whether it falls in a leap year, and how many days are in that month. It's handy when you need quick date facts like the ISO week or day-of-year without pulling out a calendar or writing throwaway code. All calculations use UTC and run instantly in your browser.
No. Date Info runs entirely in your browser and nothing you type is uploaded or stored on any server. The site is fully client-side and open source, so you can verify this yourself.
Any string that JavaScript's Date constructor accepts, such as ISO 8601 (2026-06-08), full date-times, or formats like "June 8, 2026". If the value can't be parsed it reports "Invalid date."
All output is computed in UTC. A date without a time component is treated as midnight UTC, so the weekday and day-of-year reflect the UTC date rather than your local one.
It uses the ISO 8601 week definition, where weeks start on Monday and the week containing the year's first Thursday is week 1. This can differ from week-numbering schemes that start the week on Sunday.
For each valid date it shows the weekday, day of year, ISO week number, calendar quarter, whether the year is a leap year, and the number of days in that month.