Dev tools · alternatives · 2026

24 alternatives to OI Calendar

Encrypted, decentralized alternative to Google calendar

Below are 24 products that do a similar job, ranked by how close each is in meaning and then by launch-day votes. OI Calendar launched in 2019; newer entries below may have overtaken it.

1. 1
   I built an open source web calendar inspired by the Google calendar▲232

   I love the looks and UX of the Google calendar. But I wanted to have a version I could use more freely in my own projects, still looking similar to the one from Google.

   2024 · schedule-x.dev · its alternatives →

2. 2
   hora Calendar▲132

   The Mac calendar Google never built. Fast, native, private — designed for people who find Apple Calendar too limited and everything else too much.

   Jun 2026 · horacal.app · its alternatives →

3. 3
   Google Calendar▲413

   Spend less time managing your day, now on iOS

   2015 · gmail.googleblog.com · its alternatives →

4. 4
   Button for Google Calendar™▲525

   See your daily schedule and join meetings in one-click.

   2021 · manganum.app · its alternatives →

5. 5
   Secure Calendar▲75

   Privacy respecting calendar

   2019 · securecalendar.online · its alternatives →

6. 6
   Recal.dev▲365

   Resend, but for Calendar & Scheduling. API. SDK. MCP.

   2025 · recal.dev · its alternatives →

7. 7
   Rolo Calendar▲187

   A calendar for people who don't use calendars

   2016 · rolotime.com · its alternatives →

8. 8
   Nook Calendar▲312

   Own your time, reclaim your attention

   2022 · its alternatives →

9. 9
   Automatic out-of-office calendar▲94

   Just mark your calendar as OOO, we take care of the rest

   2020 · getclockwise.com · its alternatives →

10. 10
    Notion Calendar Sync▲283

    2-way sync between Notion and your Google Calendar

    2021 · 2sync.com · its alternatives →

11. 11
    CalendarPipe▲155

    Create pipes to filter, transform, and sync events between Google Calendar, Outlook, and Apple Calendar. Build visually, describe in plain English, or write code.

    Apr 2026 · calendarpipe.com · its alternatives →

12. 12
    Add to Calendar Button v2▲159

    Let users add your events to their calendars, hustle-free

    2023 · add-to-calendar-button.com · its alternatives →

13. 13
    calendar.org▲81

    The NFT Calendar

    2022 · calendar.org · its alternatives →

14. 14
    Koalendar▲131

    Free online appointment scheduling software

    2021 · koalendar.com · its alternatives →

15. 15
    One Calendar▲14

    Your schedule, your data.

    2025 · calendar.xyehr.cn · its alternatives →

16. 16
    Calendarist▲184

    Time blocking companion for Google Calendar

    2020 · trycalendarist.com · its alternatives →

17. 17
    Timely▲176

    Pull your calendar availability in 3 seconds

    Jul 2026 · trytimely.co · its alternatives →

18. 18
    ShadowCal▲95

    Sync your Outlook Calendar to Google Calendar

    2025 · shadowcal.com · its alternatives →

19. 19
    fwd2cal▲141

    Stop adding calendar events yourself

    2024 · fwd2cal.com · its alternatives →

20. 20
    Gonebusy for Slack▲64

    A natural language Google Calendar integration for Slack

    2019 · its alternatives →

21. 21
    GRUPZ Vacation Rental Calendars▲72

    Modern, responsive iCal-synced calendar widgets for any site

    2018 · grupz.com · its alternatives →

22. 22
    Solid Calendar▲77

    Natural language calendar

    2023 · apps.apple.com · its alternatives →

23. 23
    MeetingBar 4▲76

    Join your next meeting in one click

    2023 · meetingbar.app · its alternatives →

24. 24
    FluidCalendar▲27

    Opensource Motion-Alternative Calendar & Task Management App

    2025 · fluidcalendar.com · its alternatives →

Ranked by how close each launch is in meaning, then by votes. Prices were read from each product’s own site when checked and can change. Refine with your own description →