When breaking an overnight shift, the hours are placed on the next day if the start time of the new shift is after the duty start time for the next day.  This behavior is normal because the systems posts time to the day it began. 

The Duty Day Start is one of the template display property fields and it designates the time that is the start of the day for a schedule.   Shifts beginning before this time are considered part of the previous day.  This is particularly useful when employees are scheduled to work 24-hour shifts that do not begin at midnight. 

For example, imagine that employees are scheduled from 8am-8am and an employee goes home sick at midnight.  The overtime employee brought in to cover the rest of the shift will be working from midnight to 8am.  If the Duty Day Start is set at midnight, then this overtime shift would be considered part of the next day.  On the schedule it would not display on the same day as the shifts that began at 8am, despite the fact that it is the final segment of one of those shifts.  If the Duty Day Start is set at 8am, however, this overtime shift will display on the same day as the rest of the 24-hour shifts. 

This setting affects both the Daily Roster and Times Grid views, though, for the Times Grid view, it will only matter for the first and last days shown.  The default Duty Day Start setting is midnight.