A truism of any job is: the work must get done. Sometimes that means delegating and sharing responsibilities. Sometimes it means having your day planned out in 15-minute increments. Sometimes it means being reactionary to the needs of others.
Most companies and managers like their employees to have set work hours such as Monday to Friday 8 to 5. They want their employees to feel like they can shut down on the weekends and have their dinner time be uninterrupted by the various things that could still be coming in. When you are in an office environment this timing also helps because it makes it easier to schedule the receptionists, janitorial staff, IT downtime, and all of the other various office support functions.
But the reality is that while most work tasks are most likely to occur within that window, because that’s when the vast majority of your colleagues are working, it’s certainly not absolutely true. There are occasional Wednesdays where you know beforehand there will be nothing at all required to keep the business going yet most people are still going to be at the office, in their chair, doing their best to look busy. Similarly, there will be Wednesdays where anything less than working from 6a to 8p can’t get everything completed that needs to get completed. Structured hours do not account for the natural ebbs and flows of how activities and tasks actually come in.
This is not to provide an answer to how to best manage the time of your employees but to give you a new lens to thinking about it as yet another variable that can be optimized to both make your employees happier and also make your business more efficient and productive. Office hours are often assumed to just “be what they are” but they do not have to be set in stone.