Default Alarm Lead Times
You can specify an amount of time before the start of an activity to designate when alarm notification occurs.
To set up the default alarm lead time
From the application-level menu, choose Tools, then User Preferences.
The User Preferences screen appears.
On the link bar, click Calendar.
The Calendar form appears.
From the drop-down lists for the Alarm Lead Time field, select a time between 5 and 120 minutes.
Instead of minutes, you can select hours, days, and weeks. The time that you select is the time interval before appointments or reminders that all alarms trigger.