By default events are setup to sell 24 hours in advance and close sale at midnight the day before.
This can be altered to allow sales on the day of the event or extend the length of time that is required to book before sales are closes:
To do this:
Step 1: Login to the admin area
Step 2: On the left hand navigation bar, select "Admissions" then click "Events"
Step 3: Find the event you would like to change and click it.
Step 4: On this page find the section labelled: "Must purchase  day(s) before visit"
Step 5: In the "Must purchase" box, it will most likely have a "1" in this by default; this means the customer must purchase a ticket 1 day before the event. If you'd like people to purchase tickets on the same day as the event, put a "0" in the box.
Step 6: Click save