# One Calendar vs IDRT

The clearest difference is update cadence: IDRT at every 3 days against One Calendar's fortnightly. One Calendar's advantage is device support (4 vs 1). On price, ads, in-app purchases and iOS requirement there is nothing between them.

Both are free to download. One Calendar sells 1 one-off in-app purchase and IDRT sells 8 in-app purchases, starting at $59.99 per month. Whichever you choose, the download price is not the number that matters.

One Calendar ships an update fortnightly, IDRT every 3 days. The most recent releases landed on October 20, 2026 and October 5, 2026 respectively.

## The numbers

| Metric | One Calendar | IDRT |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.8 (21K ratings)](https://appshunter.io/ios/app/one-calendar/id1238379385/reviews)** | — |
| Number of ratings | **21K** | — |
| Positive reviews | 80.7% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Fortnightly | **Every 3 days** |
| Monetization | Free with in-app purchases | — |
| Size | 89 MB | 50 MB |
| Requires iOS | **15.0** | 16.4 |
| Devices | **iPhone, iPad, iPod, Mac** | iPhone |
| Age rating | 12+ | 4+ |
| Developer | [Code Spark](https://appshunter.io/developer/1238379384) | [Skretteberg AS](https://appshunter.io/developer/1896515645) |

## What reviewers say

### One Calendar

[App page](https://appshunter.io/ios/app/one-calendar/id1238379385)

Consolidate all your digital calendars into a single, easy-to-read view. Manage appointments, events, and birthdays from various providers like Google, Outlook, iCloud, and more, all within one application.

**Highlights:** Integrates multiple calendar providers, Easy-to-read overview, Manage appointments and events, View birthdays, Cross-platform availability

**Features:** Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| OneCalendar premium | $5.99 | one-time |

**What reviewers like**

- 🚀 Easy to use
- 👍 Clean and simple interface
- 👍 Integrates multiple calendars
- 🚀 Syncs across devices
- 👍 Customizable colors and themes

**What reviewers complain about**

- 🐛 Syncing issues
- 🐛 Bugs and glitches
- 🔒 Lacks security features
- 🔋 Drains battery
- 👎 Restrictive features in free version

**Reported bugs**

- Sync errors
- Unresponsive buttons
- Incorrect time zone display
- Duplicate events
- Inability to delete future occurrences of recurring events

**Requested features**

- Multiple reminders for events
- Ability to edit recurring events
- Option to change event calendar after creation
- Printing support
- More customization options


### IDRT

[App page](https://appshunter.io/ios/app/idrt/id6798715862)

**In-app purchases (8)**

| Purchase | Price | Billing |
| --- | --- | --- |
| IDRT Basic | $59.99 | per month |
| IDRT Growth | $79.99 | per month |
| IDRT Basic | $179.99 | per 3 months |
| IDRT Growth | $229.99 | per 3 months |
| IDRT Basic | $299.99 | per 6 months |
| IDRT Growth | $449.99 | per 6 months |
| IDRT Basic | $599.99 | per year |
| IDRT Growth | $799.99 | per year |


## Frequently asked questions

### Is One Calendar free?

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

### Is IDRT free?

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

### Do One Calendar or IDRT have ads?

Neither One Calendar nor IDRT shows ads.

### Which is updated more often, One Calendar or IDRT?

One Calendar ships an update fortnightly, and IDRT every 3 days. Most recently, One Calendar was updated on October 20, 2026 and IDRT on October 5, 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.*