As per this link, shift management allows for shift rotation but the current configuration for shifts DOES NOT reflect on a calendar on the desktop when that SHIFT day is considered an OFF day. According to SHIFT setup, we can only create a weekend setting to reflect a day per week that they would not be on schedule. Secondly, ONLY one shift can be assigned per employee per week. Many times with hybrid workers shifts vary by DAY not week. Since the Attendance module shift management in the "Attendance Calendar" menu does not provide for reflection of DAY Shift variances or that OFF shifts should be reflected as "OUT" not on "Weekend" needs updating. Since most Zoho APPS get updates quarterly and this has app has not been updated to be reflective of common requirements for Modern HRIS systems.  Please update this immediately or at least schedule to do so. I would hate to leave Zoho for our HRMS as this is a simple upgrade as you already have an application called SHIFTS.

Later edited to explain further  - 

To get the calendar to reflect that the user is off we not only need to set the weekly shift, we then need to set daily shifts called "OFF" to have a physical reflection for the calendar day view to show the user is not in. This means for every user we are making any where from 3-4 shift requests and then approvals to get the weekly calendar to reflect that the end user is in for specific hours per day and when they are out of office" as a weekly shift with a weekend setting will not reflect that they are not in on the calendar view, you would need to know that this shift means only working limited dates.