In OS X it’s possible to change the highlight color. You can do this in the General ▸ Appearance panel in System Preferences. The Calendar application doesn’t use the highlight color for ‘Today’. This uses the default color blue, you can enable the system highlight color for the today selection with the following command.
Calendar (iCal)
Calendar: Change the amount of days in week view (10.8)
It is possible in Mountain Lion’s Calendar app to change the numbers of days displayed in the week view. If you want to display 14 days in the week view use this command:
Change default appointment duration in iCal (Calendar)
iCal has a feature whereby you can easily create new calendar appointments. Just click ‘+’ at the top left of the window and start typing. For example, “Friday BBQ 20:00” will create an appointment on the next Friday at 8 pm and is called “BBQ”.
Access the Debug menu in iCal
In iCal you’ll have a debug menu. In these menu are advanced options or options used for troubleshooting that don’t need to be presented to users in everyday use of the tools.