All day events
An "All Day" event is an event that lasts for an entire day. All Day events are often birthdays, anniversaries, vacations, and any other event that does not require a specific time scheduled on a given day.
You can create an All Day event by checking the "All Day" box on the "Create Event" page. Alternatively, you can click in an open space in the All Day event section for a specific day, fill in the What field in the event bubble, then click Create Event.
When you're viewing your calendar, All Day events are listed at the top of each day. You can choose to expand or collapse the section by clicking the triangle on the left side of the event grid. When the All Day event section is collapsed, you can view the All Day events for a specific day by clicking the shaded bar with the down-arrow (just beneath the date) for the day in question. A pop-out will appear, showing you all of the All Day events scheduled for that day. If an All Day event span several days, you'll see the start and end date listed as well.
Keep in mind that reminders for "All Day" events are based on 5:00 pm the day before the event (according to your current time zone). So, if you choose to receive your reminder 10 minutes before your "All Day" event on August 24th, you'll be reminded on August 23rd at 4:50 pm. Please visit the Notification section for more information on receiving Google Calendar reminders.