Users can enable or disable the visibility of special calendars, including Birthdays, where the app retrieves dates of births from Google contacts and displays birthday cards on a yearly basis, and Holidays, a country-specific calendar that displays dates of special occasions.

Over time, Google has added functionality that makes use of machine learning, including "Events from Gmail", where event information from a user's Gmail messages are automatically added to Google Calendar; "Reminders", where users add to-do activities that can be automatically updated with new information; "Smart Suggestions", where the app recommends titles, contacts, and locations when creating events; and "Goals", where users enter information on a specified personal goal, and the app automatically schedules the activity at optimal times.

The integration between Google Calendar and Gmail was praised, however, with critics writing that "all of the relevant details are there".

The feature, enabled by default, will also update events with new information based on new email messages received, such as flight delays.

[18][19] The feature was expanded in January 2017 with support for Google Fit and Apple Health, to see the progress made towards completing a goal.

[32] Some users criticized this change in early February 2025 after Google started rolling back its diversity, equity and inclusion (DEI) initiatives.

[39] Initially only available on the web and on the Android operating system, an iOS app was released on March 10, 2015.

This is a great feature for creating events that occur over and over, like a haircut or doctor's appointment, because the app remembers the phrases you use".

She complimented the integration between Google Calendar and Gmail, writing that "All of the relevant details are there, including confirmation numbers, links to the source email, even gate assignments for flights", and called it "one of my favorite parts of the app", but also noted that the feature could be turned off.

She also criticized the Smart Suggestions, writing that "in my short time using Google Calendar, the natural language support leaves a lot to be desired.

Walter called the Material Design "rather elegant and polished, with a focus on parceling off information for easy viewing, registering touches with a subtle splash on the screen, and using a lot of visuals cues", but noted that "it's not for everyone, especially if you prefer Apple's design overhaul first introduced in iOS 7.

You'll also find that some elements of Material Design don't translate well to the iPhone, such as the loss of the slide gesture to go back".