# O2 Calendar vs Mega Calendar

The clearest difference is review sentiment: Mega Calendar at 100% against O2 Calendar's 50%. O2 Calendar's advantage is in-app purchases (none vs 3) and ads (none vs shown). On price and device support there is nothing between them.

Both are free to download. Mega Calendar sells 3 in-app purchases, starting at $0.99 per month. O2 Calendar asks for nothing beyond the download.

O2 Calendar ships an update every 4 days, Mega Calendar every 2 weeks. The most recent releases landed on November 3, 2026 and November 4, 2026 respectively.

## The numbers

| Metric | O2 Calendar | Mega Calendar |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (1 ratings)](https://appshunter.io/ios/app/mega-calendar/id6496850711/reviews)** |
| Number of ratings | — | **1** |
| Positive reviews | 50.0% of reviews | **100.0% of reviews** |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 4 days** | Every 2 weeks |
| Monetization | **Free** | Free with in-app purchases |
| Size | 52 MB | 103 MB |
| Requires iOS | **9.0** | 15.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [O2 VN Tech.,JSC](https://appshunter.io/developer/1547745523) | [VU THANH](https://appshunter.io/developer/1009861172) |

## What reviewers say

### O2 Calendar

[App page](https://appshunter.io/ios/app/o2-calendar/id1547745521)

Manage your schedule with this app, offering tools for events, appointments, notes, and daily tasks. Set custom reminders for your important activities and organize your day effectively.

**Highlights:** Event creation and management, Customizable event reminders, Daily task reminders, Note-taking functionality, Appointment scheduling

**Features:** macOS Compatibility

**In-app purchases:** none


### Mega Calendar

[App page](https://appshunter.io/ios/app/mega-calendar/id6496850711)

Organize your schedule with detailed daily planning, recurring event setup, and customizable reminders. Create travel itineraries, manage to-do lists with notifications, and access all features offline. Personalize notification sounds to distinguish between events.

**Highlights:** Detailed daily planning, Recurring event setup, Customizable reminders, Travel itinerary creation, To-do list management, Offline functionality, Customizable notification sounds

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly | $0.99 | per month |
| Yearly | $3.99 | per year |
| Lifetime | $7.99 | one-time |


## Frequently asked questions

### Is O2 Calendar free?

O2 Calendar is free to download, with no in-app purchases.

### Is Mega Calendar free?

Mega Calendar is free to download, with in-app purchases available.

### Do O2 Calendar or Mega Calendar have ads?

Mega Calendar shows ads; O2 Calendar does not.

### Which is updated more often, O2 Calendar or Mega Calendar?

O2 Calendar ships an update every 4 days, and Mega Calendar every 2 weeks. Most recently, O2 Calendar was updated on November 3, 2026 and Mega Calendar on November 4, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*