Google Calendar might very well be the most popular calendar app around, according to at least one survey.It’s like the One Calendar to Rule Them All because it lets you keep multiple calendars—for personal, work, holidays, and more—in one place, using your existing Google account (one less login to remember).

The best calendars, however, aren't just functional—they're actually fun to use and help make you more productive.

For this roundup, we looked for apps that were: Google Calendar, Microsoft Outlook, and Apple Calendar (formerly known as i Cal).

If you use an Android device, chances are you already have Google Calendar installed.

The color coding for individual calendars makes it easy to see which area of your life an event applies to at-a-glance.

That means you can keep your calendar up-to-date across all your Apple devices and on the web through i Cloud (if you set up Apple Calendar to sync through i Could, that is).

This ubiquitous app can also pull in other calendars, such as Google Calendar.

In Google and Apple's cases, they're not just apps, they're also services: Places you enter and store events that other apps can connect to, where you can access and edit those events in a different interface.

Some apps also can sync with Outlook's desktop app, as well as Exchange Server, Microsoft's calendar and contacts service for the workforce.

Click or tap the plus sign ( ) to create a new event, which can include a title, location, reminder, note, plus any invitees.