# On This Date vs Interactive Quantum Mechanics

The clearest difference is in-app purchases: On This Date at none against Interactive Quantum Mechanics's 1. On This Date also leads on iOS requirement (16.2 vs 26.2). Interactive Quantum Mechanics's advantage is ads (none vs shown) and update cadence (fortnightly vs every 2 months). On price and device support there is nothing between them.

Both are free to download. Interactive Quantum Mechanics sells 1 one-off in-app purchase. On This Date asks for nothing beyond the download.

On This Date ships an update every 2 months, Interactive Quantum Mechanics fortnightly. The most recent releases landed on September 17, 2026 and October 6, 2026 respectively.

## The numbers

| Metric | On This Date | Interactive Quantum Mechanics |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | Yes | **No** |
| Update frequency | Every 2 months | **Fortnightly** |
| Size | 9 MB | 10 MB |
| Requires iOS | **16.2** | 26.2 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [Jannis Guhl](https://appshunter.io/developer/1686812636) | [Stephen Moon](https://appshunter.io/developer/6786831121) |

## What reviewers say

### On This Date

[App page](https://appshunter.io/ios/app/on-this-date/id6448892142)

**In-app purchases:** none


### Interactive Quantum Mechanics

[App page](https://appshunter.io/ios/app/interactive-quantum-mechanics/id6786831119)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Founder's Pass | $14.99 | one-time |


## Frequently asked questions

### Is On This Date free?

On This Date is free to download, with no in-app purchases.

### Is Interactive Quantum Mechanics free?

Interactive Quantum Mechanics is free to download, with in-app purchases available.

### Do On This Date or Interactive Quantum Mechanics have ads?

On This Date shows ads; Interactive Quantum Mechanics does not.

### Which is updated more often, On This Date or Interactive Quantum Mechanics?

On This Date ships an update every 2 months, and Interactive Quantum Mechanics fortnightly. Most recently, On This Date was updated on September 17, 2026 and Interactive Quantum Mechanics on October 6, 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.*