Help with logic for variable shift times.

I am trying to make it so when someone inputs a starting shift time into the admin page of the HMI, the PLC sees this change and knows what shift it is when it scans after a power cycle. I already have everything figured out except for the logic itself. I tried using limits but it gets a little confusing when you start throwing in minutes greater than zero. So, can someone show me how to set this up so that none of the shift times contradicts each other?

** I already have it programmed so it will change shifts while the machine is on, I just need to figure out how to get it to recognize the correct shift after a power cycle and first scan.

Sorry for the poor wording, I am new to this.

Tell us what platform you're working with.