Uploading a calendar from your local phone is easy. But it can't be done directly from your phone so a few extra steps are necessary.
Step 1: Log into icloud.com with your Apple account ID and password.
Step 2: Click on the Calendar icon.
Step 3: Click on the "Sharing" icon on the right side of the calendar name.
Step 4: Make this calendar "Public"
Step 5: Click the button to copy your "Public Calendar Link"
Step 6: Email this link to firstname.lastname@example.org
Next you will see the calendar app loaded, and you should see your calendars listed on the left side of the page. Select the calendar you want to export.
This will pull up some sharing options.
Click the checkbox to enable this as a public calendar. Don't worry, you can set it back to a private calendar again in a few minutes.
Click the button to copy the public calendar link.
You will need to keep your calendar public long enough for our team to import your data. After this, you can make it private again. If you want to keep your calendar private the entire time then follow these steps.
Paste the link that you copied into the address bar on a new tab, but do not press ENTER yet. Notice at the beginning of the link it starts with webcal://.
Change the "webcal://" to "https://" and now press ENTER.
This will download an iCal file that contains all your events. Upload this file below: After you upload this file you can immediately go back and unselect the "Public Calendar" option to make it private again.