Public Calendars can be managed by multiple admins. You can invite people to become admins via invitation URL links.

STEP１：Open the manage menu from your public calendar.

STEP 2 : Select Manage Members

STEP 3：Tap Members list shown in the image.

STEP 4：Obtain the invitation link by tapping the invite button.

STEP 5 : Share the URL via LINE, Facebook Messenger, Email, Twitter.