CalendarDuo vs M21
Price, ratings, monetisation and update history for both apps, side by side β with what reviewers say about each.
CalendarDuo
Easily manage and view holidays from two different countries simultaneously. This utility app offers instant switching between calendars, a dual-view display, and helpful tools like a world clock and currency exchange.
- Switch between two world calendars instantly
- Duo-view with holidays from two countries
- Daylight Saving Time dates
- Currency exchange rate
- World clock
- Add notes
Read full descriptionHide full description
** This app does not access your Contact List or Calendar. ** CalendarDuo allows users to switch between two calendars at their fingertips! CalendarDuo is the best tool for: - Frequent flyer between two countries/regions - Organizing events with family members or relatives overseas - Scheduling meetings and tasks with colleagues overseas - Planning trips to another country/region - ANYONE who needs a simple calendar! Top features - Switching between TWO world calendars INSTANTLY - Duo-view displaying ONE calendar with holidays of TWO countries/regions - User interface with multiple language selection - Daylight Saving Time (DST) dates - Currency exchange rate (for currencies available in Europe Central Bank) - World clock - Adding notes CalendarDuo is the simplest calendar youβll ever need! NEW! 2026 holidays are available now! - public holidays - bank holidays - statutory holidays - regional holidays - provincial holidays - special days NEW! 2022 World Calendars (more are coming!): - Australia - Canada - China (PRC) - France - Germany - Hong Kong - India (Maharashtra, New Delhi) - Indonesia - Italy - Japan - Macau - Malaysia - Philippines - Portugal - Singapore - South Korea - Taiwan - Thailand - United Kingdom - United States - Vatican City Holiday information is gathered from government official releases. Source details can be found on each Holiday List.
M21
Read full descriptionHide full description
An application special for the Indonesian diaspora overseas. With only one application, you can enjoy the following features: Indonesian Virtual Number (For Indonesian passport holders only) Top up for Hong Kong, Taiwan, Malaysia, and Indonesia operators OTT SMS OTT Call And a lot more To get an Indonesian Virtual Number and buy an Indonesian e-wallet voucher, customers must register and top up.
Screenshots
Verdict
The clearest difference is ads: M21 at none against CalendarDuo's shown. M21 also leads on update cadence (every 6 weeks vs every 4 months). On price, in-app purchases, device support and iOS requirement there is nothing between them.
Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
CalendarDuo ships an update every 4 months, M21 every 6 weeks. The most recent releases landed on June 24, 2026 and September 8, 2026 respectively.
| Parameter | CalendarDuo | M21 |
|---|---|---|
| Price | Free | Free |
| Positive reviews | 50.0% of reviews | β |
| Update frequency | Every 4 months | Every 6 weeks β better |
| Ads | Yes | No β better |
| In-app purchases | No | No |
| Monetization | Ad-supported | β |
| Devices | iPhone, iPad, iPod β better | iPhone, iPod |
| Requires iOS | 15.1 β better | 15.5 |
| Further details β not scored | ||
| Size | 41 MB | 115 MB |
| Age rating | 4+ | 4+ |
| Developer | Chun Lam | Telin |
In-app purchases
CalendarDuo
No in-app purchases
M21
No in-app purchases
Questions
Is CalendarDuo free?
Is M21 free?
Do CalendarDuo or M21 have ads?
Which is updated more often, CalendarDuo or M21?
Other comparisons
