Everything you need
to get started.

manyCalendars is available on all three major browser stores. Pick your browser:

• Google Chrome: Chrome Web Store
• Mozilla Firefox: Firefox Add-ons
• Microsoft Edge: Edge Add-ons

Click the install button on the store page and confirm the requested permissions. The extension requires access to read page content (for Tab Sync) and storage (to save your calendar data locally). No admin password or IT approval is needed.

After installation, manyCalendars opens a new tab with your unified calendar view. You will see an empty calendar grid and a sidebar on the left. The sidebar is where you manage all your calendar sources.

On first launch, the extension runs a brief onboarding flow:

1. Choose your preferred theme (defaults to Catppuccin Latte)
2. Set your primary timezone
3. Add your first calendar source

You can skip the onboarding and configure everything later from Settings (gear icon, top right).

Click the + Add Calendar button in the sidebar. You will see three options:

1. ICS Feed: Paste a calendar URL (the most reliable method for Google Calendar, Outlook.com, and Apple iCloud)
2. Sync Tab: Import events from an open browser tab (best for locked-down corporate calendars)
3. Manual Calendar: Create a local-only calendar for events you enter yourself

After adding a source, give it a name and pick a color. Events appear in the main calendar view immediately.

ICS (iCalendar) feeds are the standard way to subscribe to a calendar. Most calendar providers offer an ICS URL you can paste into manyCalendars. The extension fetches the feed periodically and updates your view with any new or changed events.

Google Calendar:

1. Open calendar.google.com
2. Click the gear icon, then Settings
3. In the left sidebar, select the calendar you want to share
4. Scroll to Integrate calendar
5. Copy the Secret address in iCal format
6. Paste into the extension's ICS feed field

Outlook / Microsoft 365:

1. Open Outlook on the web
2. Go to Settings (gear) then View all Outlook settings
3. Navigate to Calendar then Shared calendars
4. Under Publish a calendar, select your calendar and set permission to "Can view all details"
5. Click Publish and copy the ICS link

Apple iCloud:

1. Open icloud.com/calendar
2. Click the share icon next to the calendar name in the sidebar
3. Check Public Calendar
4. Copy the URL (it starts with webcal://)
5. Paste it into the extension. The extension automatically converts webcal:// to https://

Tab Sync reads events directly from a calendar tab open in your browser. This is the solution for corporate calendars where ICS export is disabled by IT.

How it works:

1. Open your calendar in a browser tab and sign in normally
2. Switch to Day or Week view (these show the most detail)
3. In manyCalendars, click + Add Calendar then Sync Tab
4. Select the tab from the list and give the calendar a name

The extension reads event data from the page's accessibility tree (the same data screen readers use). It re-syncs automatically every 15 minutes to keep your view current.

Supported providers:

• Microsoft Outlook (outlook.office.com, outlook.live.com)
• Google Calendar (calendar.google.com)
• Apple iCloud Calendar (icloud.com/calendar)
• Fastmail Calendar
• Zoho Calendar

If your provider is not listed, Tab Sync may still work. Try it. If the extension cannot parse the page structure, email [email protected] with the calendar URL domain and we will investigate adding support.

Manual calendars are local-only calendars where you create events yourself. They are useful for:

• Personal reminders that do not belong in any work calendar
• Placeholder events for time you want to block
• Side-project schedules you prefer to keep separate

To create a manual calendar, click + Add Calendar then Manual Calendar. Give it a name and color.

To add events, click any time slot in the calendar grid, or use the + New Event button in the toolbar. Fill in the title, start/end time, and optional notes.

Manual calendar data is stored locally in your browser's extension storage. It is never sent to any server.

Auto-blocking prevents double bookings across calendars. When an event exists on one calendar, the extension marks that time as "busy" on your other calendars. If someone tries to book over a conflict, you will see a warning.

How to enable:

1. Open Settings (gear icon)
2. Navigate to Auto-blocking
3. Toggle it on
4. Choose which calendars participate in blocking (by default, all calendars are included)

Auto-blocking is a visual indicator within the extension. It does not modify any events on the source calendars. Your Google, Outlook, and other calendar providers are never altered.

Privacy Mode replaces the interface with a neutral, generic calendar view during a screen share, so another client's meeting titles and names stay off the shared screen. It is about client confidentiality, not hiding the tool.

Default appearance: a plain, unbranded "Calendar" view with neutral colors, no product logos, and a generic "Calendar" tab title. This is the default the moment Privacy Mode is on.

Optional appearances: you can opt into an alternate look from Settings. These are never the default, and the generic view stays the standard experience.

Activation: Press Ctrl+Shift+S (Windows/Linux) or Cmd+Shift+S (Mac). You can also click the eye icon in the toolbar or enable it from Settings.

The change applies instantly via a CSS class swap (under 100ms). The browser tab title also changes to a generic "Calendar." Notifications and toasts are suppressed while Privacy Mode is active.

The extension can show browser notifications before meetings start. Reminders work across all calendar sources (ICS, tab-synced, and manual).

Configuration:

1. Open Settings then Notifications
2. Toggle Meeting reminders on
3. Set the reminder interval (5, 10, 15, or 30 minutes before)
4. Grant browser notification permission when prompted

Reminders are suppressed when Privacy Mode is active, so they will not accidentally reveal the extension during screen-sharing.

If you work with people in different timezones, enable the multi-timezone clock strip. It shows the current time in up to 4 timezones at the top of the calendar view.

Setup:

1. Open Settings then Timezones
2. Click + Add timezone
3. Search for a city or timezone name (e.g., "Pacific", "London", "Tokyo")
4. Repeat for additional timezones

The clocks update in real time. You can also hover over any time slot in the calendar grid to see the equivalent time in all configured zones.

manyCalendars supports the following keyboard shortcuts:

• Ctrl+B / Cmd+B : Toggle the sidebar
• Ctrl+Shift+S / Cmd+Shift+S : Toggle Privacy Mode
• T : Jump to today
• D : Switch to Day view
• W : Switch to Week view
• M : Switch to Month view
• N : Create a new event
• R : Refresh all calendars
• Arrow keys: Navigate between days (Day view) or weeks (Week/Month view)

Shortcuts only activate when the extension tab is focused. They do not interfere with other browser shortcuts or web pages.

manyCalendars ships with four themes from the Catppuccin palette:

• Latte (light, warm): Soft cream background with gentle contrast. Good for daytime use and bright environments.
• Frappe (mid-dark): Muted blue-gray background. A comfortable middle ground for all-day use.
• Macchiato (dark): Deeper tones with slightly warm undertones. Reduces eye strain in dim lighting.
• Mocha (darkest): Near-black background with high-contrast text. Best for working at night or in very dark rooms.

To change your theme, open Settings then Appearance and select from the theme gallery. The change applies instantly with no reload required.

Each calendar source can have its own color. This makes it easy to distinguish events at a glance (for example, blue for your personal Google Calendar and orange for your corporate Outlook).

To change a calendar's color:

1. In the sidebar, right-click (or long-press on mobile) the calendar name
2. Select Change color
3. Pick from the preset palette or enter a custom hex code

Color changes are reflected immediately in the calendar grid, sidebar, and any reminder notifications.

Common causes and fixes:

• 404 Not Found: The ICS URL may have changed. Re-export the URL from your calendar provider and update it in the extension.
• CORS blocked: Some calendar providers restrict cross-origin requests. The extension routes ICS fetches through its background service worker to avoid CORS issues, but certain corporate proxies may still block requests. Try accessing the ICS URL directly in a browser tab to verify it works.
• Authentication required: If the ICS URL requires a login, it will not work as a feed. Use the "secret" or "private" URL variant instead, which includes an authentication token.
• Empty calendar: Verify the source calendar actually has events in the current date range. Some ICS feeds only include events from the last 30 days.

After fixing the URL, click the refresh icon next to the calendar in the sidebar to re-fetch immediately.

When you see a "Needs sign-in" indicator next to a tab-synced calendar, it means the browser session for that calendar provider has expired.

To fix:

1. Open the calendar provider in any browser tab (e.g., outlook.office.com)
2. Sign in with your credentials
3. Return to manyCalendars and click Refresh All, or wait for the next automatic sync (up to 15 minutes)

Most enterprise Outlook sessions expire every 8 to 24 hours depending on your IT policy. There is no way to prevent this expiration from the extension's side; it is controlled by your organization's identity provider.

If a calendar source syncs successfully (green dot) but events do not appear in the grid, check these:

• Calendar visibility: Make sure the calendar is toggled on (visible) in the sidebar. A dimmed calendar name means it is hidden.
• Date range: Navigate to the date where events exist. The extension only renders events within the visible date range.
• Timezone mismatch: If events appear at the wrong time or seem to be missing, check your timezone setting in Settings. A misconfigured timezone can shift events outside the visible window.
• All-day events: All-day events appear in a separate strip at the top of the Day and Week views. Scroll up if you do not see them.

If none of these resolve the issue, open DevTools (F12), check the Console tab for errors, and email a screenshot to [email protected].