ISO-8601 week number for any date, plus that week's Monday-to-Sunday range.
ISO 8601: weeks start on Monday; week 1 is the week containing January's first Thursday
2026-01-01 falls in ISO week 1 of 2026.
The ISO standard (used across Europe and by most software) starts weeks on Monday and assigns week 1 to the week containing the year's first Thursday. The US convention instead numbers weeks from Sunday with week 1 starting Jan 1, which can disagree by one — this calculator follows ISO.
52, occasionally 53 — a 53-week year happens whenever Jan 1 falls on a Thursday (or Wednesday in a leap year).
Exact age in years, months and days from any birth date — plus total days and next birthday countdown.
Add or subtract days, weeks, months or years from a date to find deadlines and future dates.
Time between a start and end clock time, with optional break deduction for timesheets.
Count working days between two dates or find the date N business days away, skipping weekends.
Count days between two dates, with inclusive totals, weekday counts and weekend counts.
Estimate monthly mortgage payments including principal, interest, taxes and insurance for any home price.