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The answer to your question is iCloud.
Setup an iCloud account on your computer and devices and all of your information will be synchronized between them.
The articles below will explain more:
A calendar that keeps up with you.
Update your schedule in one place and see your changes everywhere. When you have multiple devices, iCloud updates them with your most recent appointments — saving you time for all the other things you have going on. You can also share calendars with other iCloud users. A datebook your whole family can add to. Or a team schedule that every player can access. As soon as someone adds or edits an event, iCloud updates it wirelessly on everyone’s devices.
I hope this information helps ....
Have a great day!