Google Calendar displays dates, events, and time slots by default, but not week numbers. For professionals who plan deliveries by week, parents in shared custody who think in even and odd weeks, or project managers who schedule their sprints on a weekly calendar, this absence complicates reading the schedule. However, the option exists in the settings, both on computer and mobile, and activating it takes less than a minute.
ISO 8601 Standard and Week Numbering in Google Calendar
Before checking the box in the settings, it’s important to understand which numbering system Google Calendar uses. The ISO 8601 standard defines week 1 as the one that contains the first Thursday of January. This calculation, adopted in most European countries, can produce a week 53 in certain years.
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For several years, there was a discrepancy between the web version of Google Calendar and the Android app. The desktop interface followed the ISO 8601 standard, while the mobile app sometimes calculated week numbers according to a different rule (the week containing January 1 = week 1). Since 2024, Google has harmonized the algorithm between desktop and mobile, which has eliminated most of these discrepancies.
This point remains useful to keep in mind if you are using an older Android device that has not received the latest updates to the app. In this case, the numbers displayed on your phone may still differ from those on your computer.
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For those managing even and odd weeks in a custody or team rotation context, a detailed guide explains how to display week numbers on Google Calendar with the settings tailored to this specific need.
Setting Week Numbers on Google Calendar Web Version
On a computer, the process goes through the general settings of the calendar. Here are the concrete steps.
- Open Google Calendar in your browser (calendar.google.com), then click on the gear icon in the top right corner and select “Settings”.
- In the left sidebar menu, stay in the “General” section and look for the “Display Options” section.
- Check the box “Show week numbers”. The change applies immediately, without reloading the page.
The numbers then appear in the mini-calendar located on the left side of the screen. In monthly view, each week line displays its number at the beginning of the row. The numbers remain visible in all views (day, week, month, schedule), but their exact location varies depending on the selected display mode.
A point noted by several users on Google forums: when the left sidebar is minimized (menu closed), the week numbers may disappear from the main display. Simply reopening the mini-calendar will bring them back. Google has not changed this behavior since the first reports in 2019.
Activating Week Numbers on the Android and iOS Mobile App
On Android, open the Google Calendar app, tap the hamburger menu (three horizontal lines in the top left), then scroll down to “Settings”. Select “General” and enable the “Show week number” option. The numbers will then appear in the monthly view, to the left of each week line.
On iOS, the behavior differs slightly. The Google Calendar app now aligns with the system setting of Apple’s native calendar. If you have enabled week numbers in the iOS settings (Settings, Calendar, Week Numbers), the Google Calendar app will automatically pick them up. This synchronization with Apple’s system was gradually introduced between 2023 and 2025.
For iOS users who still do not see the numbers appearing, updating the app via the App Store usually resolves the issue. Recent release notes mention fixes related to localization and date formats.
Google Workspace: Enforcing Week Number Display Across an Organization
In a professional setting with Google Workspace, each employee can activate the option individually. However, administrators have an additional lever. Since the updates to the admin console rolled out in 2023-2024, admin policies allow enforcing the default display of week numbers for all users in a domain.
This feature can be found in the Google admin console, under Google Calendar settings (section “Policies”). The advantage is twofold: new accounts created in the organization automatically inherit the setting, and existing users no longer need to intervene in their personal settings.
For companies that operate with weekly schedules (logistics, construction, industrial maintenance), this centralized deployment avoids misunderstandings between collaborators who might not be referring to the same week number.
Known Limitations and Third-Party Applications Related to Google Calendar
The display of week numbers in Google Calendar remains a local display option. The numbers do not integrate into shared events or invitations. When you send an invitation to a colleague, the week number does not appear in the body of the invitation, even if both parties have activated the option.
Some third-party scheduling applications that synchronize with Google Calendar, such as Koalendar or booking tools, display their own week numbers based on the ISO 8601 standard. This works independently of the setting activated in Google Calendar. The available data does not confirm that all these third-party tools consistently adhere to the same numbering standard as Google.
For users synchronizing Google Calendar with Outlook, the week numbering depends on the setting configured in each application. Both services calculate the numbers according to rules that may differ based on region and chosen language settings. Checking the consistency between the two calendars remains a useful precaution at the beginning of the year, when discrepancies in numbering are most frequent.
Activating week numbers on Google Calendar comes down to checking a box, but its scope depends on the context: personal use, multi-device synchronization, or enterprise deployment. The most reliable setting remains the one made directly in the web settings, which then propagates to other interfaces connected to the same Google account.