As there is no manual "End of Day" sequence in the PMS, and you are not required to press a "Night Audit" button, the date will rollover automatically at 12:00AM midnight each night, along with the system clock of your computer. At this time, the PMS will post the following day's Room & Tax to all in-house reservations.

Since many Front Desk operations are 24 hours, and the typical industry standard is to "rollover" at or around 3:00AM, the "Rollover" function in the PMS is a way of emulating this to minimize interruptions in regular procedures.  

For example, if a guest arrives at 2am, most properties will want to check that guest in and charge them for the current night, but because it is after midnight, the system will already be on the new business day. The Rollover in the PMS allows you to set a "grace period" where you are still able to check the guest into the previous business day, and charge the room & tax for the current night to the correct date in the system.  

If a rollover time of 3:00AM is set, then a guest could be checked into the previous business day from any time after midnight, up to 2:59:59am. At 3:00AM, the PMS will officially consider the business date to have rolled over, and other manual steps will need to be taken to check the guest in.

For detailed information on the Rollover tab and how it works, please see the article Understanding the Rollover Period in the PMS in the Night Audit manual.