You can download Google Calendar for Android and iOS devices. Moreover, it is completely free to download and use.
Thanks to its user-friendly interface, it can automatically add events from your emails to your calendar, fill in the blanks for you and sync all of your devices. It may have slightly fewer features than the apps described below, but it is ideal for those who actively use Gmail and other Google apps.
One of the most popular and widely used cloud calendars is the Google Calendar.
