If you have access to, or share multiple calendars and keep them ticked to show at all times, then you can improve the performance yourself by un-ticking calendars when you don’t need to view them.
The more calendars you have open the more data needs to be retrieved, the data is being sent and retrieved to a location off campus (from Dublin), so inevitably there will be some delay to retrieve/update this data.
We suggest you only have your calendar ticked as default and tick others only when you need to look at them.
Please Note: The more calendars you have open the slower your email mailbox will function. So tick to see calendars as and when you require them and un-tick them before moving back to your inbox view. Outlook will always want ONE calendar to stay visible (but it can be any calendar you have access to).
It should also be noted that calendars with a lot of entries will also be slower to respond to actions. So consider viewing heavily scheduled calendars on their own as much as possible and ensure to close them when you do not need to activately look at them.