The following KB details a solution for an issue where a user/admin may observe that the on-call schedule is not displaying properly when there is an overlapping schedule.
User has an on-call schedule shift for after hours support which starts on a Friday from 16:00 - 7:59:59 AM Saturday
User also has another schedule shift for after hours support on Saturday that goes from 08:00 - 7:59:59 AM Sunday
When this scheduled is viewed from a calendar the user/admin will see a discrepancy where the overlapping shift for Friday that shows up on Saturday displays the user is working from Friday 00:00 - 23:59 which is incorrect. Here is a screen shot of this behavior.
The reason for the incorrect display is because the schedule for after hours support on Friday rounds the end time up when the time is a second before the next hour.
To prevent this from occurring the user/admin must set the schedule entry to end at a time that will not round to the next hour. This can be configured for 7:59:58 instead. Once this is done the calendar entry will now display correctly.