Google Calendar

Link Android
Link IOS

The first app or apps in this case I’m going to refer is your Google Calendar app or Your Eye Calendar app. Both of these apps are free. They mostly have the same capabilities although the design is a little bit different. The good thing about Your Eye Calendar app or Google Calendar is that they sync between all of your devices, they are absolutely free, there’s no premium version required, and they are detailed enough for you to organize all of your tasks and all of your events.