Week Number & Date Calculator

Week number lookup and date calculations in one place: see the current ISO reference, check a date or find the day a chosen number of days away.

How it works
1. Read the current week and its Monday-to-Sunday dates on the opening screen.
2. Enter a date, or select a week together with its year.
3. Calculate a span and choose whether to include the final day.

Ideal for
For delivery schedules, weekly work plans and checking birthdays. When a message refers to a numbered week rather than a date, look up its Monday and Sunday before adding it to your plans. The numbering follows ISO weeks, which may differ from the convention used in your local calendar.

Features
The current ISO reference appears in large type as soon as you open the app, followed by the dates from Monday to Sunday and the number of weeks in the current year.

The "Current week" widget puts the reference on your home screen. It updates at midnight and shows no banner.

Week numbers
→ ISO reference and weekday for any date from year 1 to 9999,
→ all days from Monday to Sunday for a chosen number and year,
→ whether a year has 52 or 53 weeks.

Date calculator
→ days between two dates, optionally including the end date, plus the same span in weeks and days and the weekdays from Monday to Friday,
→ a date plus or minus any number of days, with the weekday and week number of the result.

"Use today" fills any date field with today's date. Leap years are taken into account. Public holidays are not subtracted from the weekdays because they differ from region to region.

Weeks are counted according to ISO 8601: the week starts on Monday, and week 1 is the week with the first Thursday in January.

Also in the app: an age calculator with your exact age and next birthday, a countdown to any date, anniversaries, a birthday calendar for the birthdays you save and the church year with Easter Sunday, Pentecost Sunday and the First Sunday of Advent.

New in 1.3.0: Edit birthdays, repeat events, search and mark favorites. Photos, notes, reminders and local backups. .ics files for all-day events, text and image sharing. Regional calendar rules and custom working days. Month and year views. Age comparison and wedding lists. Orthodox Easter. Adjustable contrast and text size.

Your benefits
The week calculator turns a week reference into actual dates. Use the day counter to check a gap without counting individual calendar squares. Near New Year, read the displayed week-year carefully: it can differ from the calendar year of the selected day. For a work deadline, remember that the weekday count covers Monday through Friday without subtracting local public holidays. Check those dates separately when the distinction matters.

A slim banner at the bottom is the only advertising, so there are no annoying ads: no pop-ups, no videos. You don't need an account. Your entries and saved birthdays stay on your device only and are not sent to us. Week numbers and results are provided without guarantee. A one-time purchase removes the banner permanently.

Provider: Nelten Public GmbH, Dresden, Germany

Recent changes:

New in 1.3.0: Edit birthdays, repeat events, search and mark favorites. Photos, notes, reminders and local backups. .ics files for all-day events, text and image sharing. Regional calendar rules and custom working days. Month and year views. Age comparison and wedding lists. Orthodox Easter. Adjustable contrast and text size.