# Check Calendar vs OneImportantThing

The clearest difference is update cadence: Check Calendar at every 4 days against OneImportantThing's every 3 weeks. Check Calendar also leads on iOS requirement (15.1 vs 17.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Check Calendar sells 1 one-off in-app purchase and OneImportantThing sells 2 in-app purchases, starting at $1.99 per month. Whichever you choose, the download price is not the number that matters.

Check Calendar ships an update every 4 days, OneImportantThing every 3 weeks. The most recent releases landed on November 7, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | Check Calendar | OneImportantThing |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.7 (1.6K ratings)](https://appshunter.io/ios/app/check-calendar-habit-tracker/id1563837295/reviews)** | — |
| Number of ratings | **1.6K** | — |
| Positive reviews | 53.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 4 days** | Every 3 weeks |
| Monetization | Free with in-app purchases | — |
| Size | 58 MB | 6 MB |
| Requires iOS | **15.1** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [naoki otsu](https://appshunter.io/developer/1082476153) | [Hoshaiah Domingo](https://appshunter.io/developer/1860535479) |

## What reviewers say

### Check Calendar

[App page](https://appshunter.io/ios/app/check-calendar-habit-tracker/id1563837295)

Track your daily habits by marking them on a calendar with one-tap check-offs. Customize your experience with notes, unlimited categories, emojis, and color themes. Visualize progress with reports and receive timely notifications to stay on track.

**Highlights:** One-tap calendar check-offs, Unlimited habit categories, Customizable emojis and colors, Progress reports and graphs, Notifications and reminders, Data backup and restore, Widget support

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium (Pay Once) | $4.99 | one-time |

**What reviewers like**

- 👍 Simple and easy to use
- ✅ Effective for tracking habits
- 📅 Convenient calendar view
- 🎨 Customizable icons and emojis

**What reviewers complain about**

- 💰 Paid app with limited free trial
- 🔒 Lack of free version options
- 🔄 Data loss on device change
- 🤔 Unclear pricing and subscription model

**Reported bugs**

- Inconsistent date tracking
- Syncing issues between devices
- Unexpected loss of data and progress

**Requested features**

- Add widget support
- Implement reminder/notification system
- Provide more data visualization and analytics
- Allow selective clearing of check marks


### OneImportantThing

[App page](https://appshunter.io/ios/app/oneimportantthing/id6760181640)

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly Premium | $1.99 | per month |
| Lifetime Premium | $4.99 | one-time |


## Frequently asked questions

### Is Check Calendar free?

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

### Is OneImportantThing free?

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

### Do Check Calendar or OneImportantThing have ads?

Neither Check Calendar nor OneImportantThing shows ads.

### Which is updated more often, Check Calendar or OneImportantThing?

Check Calendar ships an update every 4 days, and OneImportantThing every 3 weeks. Most recently, Check Calendar was updated on November 7, 2026 and OneImportantThing on October 31, 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.*