Home / Calendar & Time / Merge Calendar Files

Merge Calendar Files

Combine ICS calendars into one, remove duplicates and keep only a date range or events with a word.

Free, no uploads, no sign-up. Runs 100% in your browser.

How Merge Calendar Files works

Worked out in your browser with your device clock and time zone. Calendar files follow the iCalendar standard (RFC 5545), so Google, Apple and Outlook all open them. Repeating events and time zone definitions are carried over whole.

Input: ICS. Output: ICS.

How to use Merge Calendar Files

1. Drop the calendars.
2. Pick how duplicates are found.
3. Filter by dates or a word.
4. Download the merged file.

Tips

• Times use your device time zone. Calendar files store times in UTC, so everyone sees their own local time.
• ICS files open in Google Calendar, Apple Calendar and Outlook.

Merge Calendar Files FAQ

Are my files uploaded?

No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.

Is it free? Are there limits or watermarks?

Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.

Does it work offline?

Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

Related tools

• Calendar File Viewer (ICS): Open ICS calendar files and invites as an agenda, search them, and export to CSV, JSON or Markdown.
• Calendar Event Maker (ICS): Make an .ics invite with reminders and repeats, plus Add to Google and Outlook calendar links.
• Spreadsheet to Calendar: Turn a CSV or Excel schedule into an ICS file you can import into Google, Apple or Outlook calendar.
• Recurring Dates & RRULE: Build or explain a repeat rule like "last Friday of every month" and list every date it falls on.