Where it is a three-shift working, the ideal way is to change the shift timing every week in a cyclical manner (i.e., A shift employees go to B shift, B goes to C and C goes to A shift and the cycle gets repeated). This helps in regulating the continuity and does not cause any metabolical or physical//mental strain on the employee. However, there are several cases where an employee expresses a preference for being retained in a particular shift like the night shift for a long duration of time, There is no illegality in this arrangement. There is a caution, continuing in an odd-hour shift for a long duration is known to have resulted in behaviour distortions and other psychic issues