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Find the Week of the Year

Find the ISO-8601 week number (weeks start Monday) for each calendar date. Runs entirely in your browser, so your data never leaves your device.

0 chars · 0 lines

Output

The result appears here as you type.

How to use Find the Week of the Year

  1. 1. Paste your dates. Paste one calendar date per line into the input pane, such as 2026-07-14. Each date is checked independently against the ISO week calendar.
  2. 2. Read the week number. The tool applies the ISO 8601 rule, where weeks start on Monday and the first week of the year is the one containing the year's first Thursday.
  3. 3. Copy the results. Copy the list of week numbers from the output pane, each line corresponding to the date in the same position from your input.

When to use Find the Week of the Year

Find the Week of the Year computes the ISO 8601 week number for any calendar date, the numbering used in project planning tools, European business calendars, and shipping schedules. It avoids the ambiguity of casually counting weeks from January 1.

  • Filling in a project timeline. A project manager building a Gantt chart labeled by week number wants to confirm which ISO week a milestone date falls into before publishing the schedule.
  • Matching a manufacturer's date code. A product's date code references a week number rather than a calendar date, and converting a known date to its ISO week confirms which batch it corresponds to.
  • Reconciling a European business report. A quarterly report using ISO week numbers instead of calendar dates needs each entry's actual date converted to confirm the reporting period lines up correctly.
  • Checking a payroll cycle. A biweekly payroll system references pay periods by ISO week number, and confirming which week a given date falls in verifies an employee's pay period assignment.

Examples

Mid-July

Input

2026-07-14

Output

29

Several dates at once

Input

2026-01-01
2027-01-01

Output

1
53

About the Find the Week of the Year tool

Find the Week of the Year is a free online tool that works entirely inside your web browser. Find the ISO-8601 week number (weeks start Monday) for each calendar date. Because the processing happens on your own device, nothing you enter is uploaded, logged or stored anywhere.

This page is one of 90 Time utilities on EditSafely. Each one does a single job well, and all of them follow the same rule: your input stays on your machine.

There is nothing to configure. Provide the input and the result appears on its own. 2 worked examples further down the page show exactly what the tool produces for real inputs.

Because nothing leaves your device, the tool is suitable for sensitive content such as internal documents, credentials or customer data. It also responds instantly, since every keystroke is handled on your own machine rather than by a remote API.

Frequently asked questions

Is Find the Week of the Year free to use?

Yes, it is completely free. All 2,658 tools on EditSafely work without an account, a subscription or usage limits.

Is it safe to paste sensitive or confidential data?

Everything happens locally. Your browser downloads the tool's code once, then does all the processing itself; nothing you enter is transmitted, stored or logged. You can even go offline after the page loads and it will still work.

How much text can I process at once?

There is no fixed limit. Because the work happens on your own device rather than on a shared server, the practical ceiling is your machine's memory, which comfortably handles inputs far larger than typical online tools allow.

Do I need to sign up or install anything?

No. The tool works in any modern browser on desktop, tablet or phone. There is no account to create, no extension to add and no software to install.

How do I use the result?

The output panel has a one-click copy button, and you can keep refining the input while you work; the result updates in place as you type.

Related tools

All Time Tools →

Find the Day of the Year

Find the ordinal day number (1-366) within the year for each calendar date.

Find the Day of the Week

Name the weekday for each calendar date you paste in.

Find the Date by Day of the Year

Turn an ordinal day number (1-366) back into a calendar date for a chosen year.

Find the Difference Between Dates

Count the days between two calendar dates on each line (also shown broken down into years, months and days).