Reminders are very important which will remind important things such as meetings, appointments, etc. By default, Outlook sets 15 minutes before the events to remind you, but you can change this to a longer or shorter time based on your preferences. Please see the steps below for details:
Step 1: Click the "File" tab from the Ribbon;
Step 2: Choose "Options" from the left navigation to open the "Outlook Options" dialog box;
Step 3: Click "Calendar" from the left navigation bar;
Step 4: Check the "Default reminders" box in the "Calendar options" section, and select (or type) a time from the drop-down list;
Step 5: Click "OK" to close the "Outlook Options" window.