I created calendar event through admin side, It will be showing standard calendar events. Now I created another event through User A, He is standard user profile. But my doubt is User A already created one calendar event, It can't showing Admin side. Why? Administrator have all permissions access to view the all users events. I give sharing access of calendar 'Show Details and Add Events' in Organization Wide Default. Why it can't access to admin user? Could anybody please help on this.
Basically you need to change the calendar to the user's calendar you want to see:
Click Change to switch users or calendars.
By default your admin user sees his own calendar in a Single-User View. So you need you switch it to be able to see other's user calendar in a Single-User View.