
CalendarZ
Calendarific
Countries, cities, timezones, holidays, currencies, airports — unified in a single, interconnected API. Stop juggling 6 APIs for global data.

Google Calendar
Morgen.so
Calendar Lock PEA
Apple Calendar
Etar
Microsoft Outlook
Rainlendar
A simple calendar with events (optional recurring and reminders), week numbers and a customizable...

Which is more popular?
Based on our record, Simple Calendar seems to be more popular. It has been mentioned 100 times since March 2021.
Website, pricing, platforms and company facts side by side.
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| Website | worlddataapi.com | simplemobiletools.com |
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| Company | 2026 | — |
| Listed in |
What each product offers, as listed by its team.


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Why this product is good
Recommended for
Overall verdict
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How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing World Data API and Simple Calendar.
World Data API's answer
It bundles reference data that usually requires 5+ separate integrations. Countries, timezones, holidays, currencies, airports, astronomy - all with consistent response formats and cross-linked identifiers. Query a country, get its IANA timezones. Query an airport, get its country's emergency numbers. One API key instead of managing credentials for Calendarific, TimezoneDB, REST Countries, and whatever you cobbled together for power plug data.
World Data API's answer
Depends what you're building. If you only need holidays, Nager.Date is free and covers Europe well. If you only need timezones, there are simpler options. But if your app touches multiple data types - say, a scheduling tool that needs holidays AND business day calculations AND timezone conversion - you're otherwise looking at integrating 4+ APIs with different auth, different pagination, different update schedules. That's the problem we solve.
World Data API's answer
Developers building apps where international data is a means to an end, not the product itself. Fintech teams who need business day math but don't want to maintain holiday calendars. E-commerce platforms calculating delivery dates. Travel apps showing adapter types and emergency numbers. Anyone who's wired up REST Countries, realized it doesn't have power plugs, and started Googling "power plug API" before giving up and making a spreadsheet.
World Data API's answer
Built it because I kept solving the same problem. Every project that needed "just a little country data" turned into integrating three APIs, writing adapters, and maintaining update scripts. The data exists - it's just scattered across incompatible sources. World Data API consolidates it.
World Data API's answer
Fullstack Rust for both backend, frontend, and the data sourcing layer. Data sourced from ISO standards, IANA timezone database, official government holiday calendars, and other similar authoritative sources.
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External articles and on-site reviews we used to compare the two products.


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Keep it simple with Simple File Manager Pro. Like Solid Explorer, the app is designed within the Material Design schematic, including using one floating action button to add a new file or folder. Simple File Manager...
Simple might be as simple does, but that doesn’t always have to be an insult. In the case of Simple Calendar, it wears its simplicity on its sleeve, proud for the world to see it in all its glory. Simple Calendar is...
Recommendations tracked on public social media and blogs since March 2021.


Tracking World Data API since Jan 2026.
There's https://simplemobiletools.com, who are doing their job to close that delta (not affiliated with them). - Source: Hacker News / 8 months ago
Simple Music Player (version 5.18.3): Clean music player with a customizable widget, sleep timer, battery saver. Source: almost 3 years ago
Simple App Launcher (version 5.11.4): A customizable holder for your favorite apps, reorder icons as you wish. Source: about 3 years ago
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