Caffeinated Calendar vs OneCalendar

OneCalendar is a genuinely good app, and this page is not going to pretend otherwise. It’s a mature, polished calendar aggregator that connects directly to your providers, runs no telemetry, and has earned its millions of downloads. I paid for the premium unlock on iOS and on Android, used it as my daily calendar, and I still like it.

I built Caffeinated Calendar anyway, because of one thing OneCalendar couldn’t do.

My wife and I share a family calendar, but her personal calendar is a different story. It has her own reminders on it, the kind of thing I have no business seeing on my phone all day. The problem is that her personal calendar also has the doctor’s appointments, the dog grooming, the kids’ appointments, and a dozen other things that never make it onto the shared family calendar. With OneCalendar I had two options: connect her whole calendar and see everything, including the parts that aren’t mine to see, or not connect it and miss the appointments that actually affect my week. There was no in-between, because OneCalendar has no local event filtering.

That in-between is the entire reason Caffeinated Calendar exists. So if you already use and like OneCalendar, this page is mostly about whether that one capability is worth a switch for you. For a lot of people it won’t be, and that’s a fair answer.

Platform support

Event Filters and Calendar Groups

This is the section that matters. It’s the reason this comparison exists at all.

Event Filters. A filter is a rule that hides or dims individual events inside a calendar you can otherwise see. It is entirely client-side and view-only: the underlying event is never modified, and the person who owns that calendar is not affected in any way. This is the exact problem from the intro. I can connect my wife’s personal calendar, filter out the parts that aren’t mine to see, and keep the doctor’s appointments and the kids’ schedule that actually affect my week. OneCalendar’s only option is to show a whole calendar or hide a whole calendar. There is no in-between, and that in-between is the whole point.

The filter engine has four rule types:

• Pattern: match on title, description, or location, by “contains” or exact match, case-sensitive or not, with multiple patterns per rule.
• Time-based: match by an exact start time, a time range, and/or specific days of the week, optionally restricted to recurring events only.
• Specific event: target one event and its entire recurring series by identity, created in a single tap from the event’s detail screen.
• All-day: match all-day events, optionally only recurring ones (useful for hiding a rotating on-call banner).

Every rule either hides the event (gone from the view) or dims it (faded but still visible, so you know it exists without it competing for your attention). Rules carry a priority order, so when more than one could apply you decide which wins. Each rule is scoped either to specific calendars or to all of them. You can disable a rule without deleting it. Hidden events automatically stop firing reminders, and you can optionally silence reminders for dimmed events too. Home screen widgets honor every one of these rules.

Calendar Groups. A Calendar Group is a named subset of your calendars that you switch between for context: a “Work” group, a “Personal” group, a “Family” group. Each group can carry its own accent color, you reorder them by dragging, and they appear as one-tap chips in the navigation drawer. Switching a group re-scopes every calendar view at once. OneCalendar lets you toggle individual calendars on and off, but those toggles aren’t saved, named sets you switch between.

Calendar source support

Tasks

OneCalendar doesn’t do tasks. That isn’t a criticism of the design, it’s just scope: it’s a calendar and it stays a calendar. If you want tasks alongside it, OneCalendar’s answer is a separate app called OneTask (Android, iOS, and Windows), which has its own in-app purchases.

In my experience OneTask is functional but feels built to round out a lineup rather than to be the best task app you’ve used. That’s partly a matter of preference, and if a second dedicated app with its own purchases doesn’t bother you, it gets the job done.

Caffeinated Calendar puts tasks inside the calendar itself, with no second app and no second set of purchases. Tasks carry due and start dates, priorities, percent-complete, categories, and nested subtasks, and they appear in the Agenda and Day views and in the home screen widgets, on every platform Caffeinated Calendar runs on.

Pricing and the cost model

Neither of these apps is funded by your data. That’s worth saying clearly: OneCalendar connects directly to your providers and runs no telemetry, same as Caffeinated Calendar. The difference is the shape of what you pay for.

OneCalendar is free to use, with a one-time premium unlock that adds things like appointment colors, search, theming, immediate sync, and longer history. The catch is that the premium license is per platform group. I paid for it once on iOS and again on Android, because they’re separate stores and separate licenses. If you use it on Windows too, that’s a third purchase.

Caffeinated Calendar takes a different shape. Every feature in the app works for free, on every device, on every platform, with nothing gated. Colors, search, themes, history: all free, everywhere. The only thing you ever pay for is an optional subscription that adds cross-device sync of your settings and multi-user sharing, and that one subscription covers every platform at once rather than being purchased per store.

How Caffeinated thinks about subscriptions

OneCalendar’s one-time model is fair, and I want to explain why Caffeinated Calendar doesn’t simply copy it, because the difference is deliberate.

Every feature in Caffeinated Calendar (and every other app in the Caffeinated suite) works for free, on every device, on every platform, forever. The app you install is the full app. There are no locked menu items, no “Pro” badges, no nag screens, no ads, and no upsells inside the product. In that sense it asks less of you up front than OneCalendar’s premium unlock does.

The one thing a one-time purchase can’t fund is an ongoing service. Cross-device sync of your filters, calendar groups, account credentials, and native Caffeinated calendars, plus multi-user sharing, requires servers that cost money every month to run. Charging a subscription for exactly that, and nothing else, is how the app itself stays completely free and unlimited. Everything that doesn’t need a server runs locally and talks directly to your calendar providers, so your remote calendars keep syncing through their own back ends whether you subscribe or not.

The same subscription covers the full Caffeinated suite, not just Calendar, and never asks you to upgrade a tier to unlock a feature inside any of them. And if you only use one device, you can use any Caffeinated app indefinitely without ever paying for it.

What Caffeinated Calendar doesn't have

• Maturity. OneCalendar has years of polish and millions of users behind it. Caffeinated Calendar is newer and you will find rough edges OneCalendar doesn’t have.
• A true one-time purchase. If you are firmly anti-subscription and live on a single platform, OneCalendar’s pay-once premium is a model Caffeinated Calendar deliberately doesn’t offer for sync.
• The long list of named provider presets. Adding a niche provider in OneCalendar is often a labeled, two-tap setup; in Caffeinated Calendar it may mean entering a CalDAV URL.
• A web version. Neither app’s strength, but worth noting Caffeinated Calendar has no browser version at all.