Number of resource calendars in the installation.
The connection to the server
Number of appointments in each calendar.
Outlook performance. Calendar Browser can only read the calendars in the same way as Outlook does, which means that everything you do to improve performance in Outlook also is an improvement for Calendar Browser.
Number of views selected for the Overview in the Calendar Browsersettings, first tab.If the option “Show calendars images in Overview” is selected the loading will take longer.