Hi

Since Event calendar is based on standard ASP.NET calendar, you can take advantage of skins. Appropriate skin file is located in: '~/App_Themes/folder_with_the_same_name_as_your_main_css_stylesheet/default.skin'. You'll see that there is definition of calendar with skinID EventCalendar, which is also referenced in the Event calendar webpart. This way you can then change calendar's attributes and CSS classes. You can refer to them in your CSS stylesheet afterwards. Furthermore, Firebug and HTML source code inspecting will be helpful for you.

Best regards,
Ivana Tomanickova