When do most employees work overtimes at the office? Do they go in early or do they stay late after work? If you want to catch them, what would be the best time to find them? Data from our work measurement studies provides some insights.

If one considers a “normal” work week for knowledge workers to begin at 9:00 a.m. and finish at 5:00 p.m., this would add up to 40 hours per week, including lunch and breaks.

We examined time and motion strudy data from employees who tracked their own time using the innovative TimeCorder device. All of the data is anonymous, so employees felt comfortable in tracking the time they spent on work activities. Across a broad range of industries, our data shows that the average employee works 46.7 hours per week. This means that they work just over an hour per day extra, assuming a base of a 40-hour week.

For this time study analysis, we looked at people who work more overtime hours than the average . Examining the pattern of activity among 235 employees who work over 50 hours, TimeCorder data shows the average time worked for this subset of workers is 55.5 hours per week. 72% of these hours (or 40 hours per week) are completed during the 9:00 a.m. to 5:00 p.m. period. Of the remainder, 19% occur prior to 9:00 a.m. and only 9% occur after 5:00 p.m.

So overtime work occurs more in the morning than in the evening.

An expanded work day shows the same pattern. When the bookends of the day are extended one hour earlier and one hour later, the result is a work day that stretches from 8:00 a.m. in the morning until 6:00 p.m. at night. Among those with high overtime hours, the total time worked during this period now represents 85% of all hours. Earlier in the morning than that, hours worked are equivalent to 10% of the total. Meanwhile later in the evening, overtime hours represent just 5% of the total.

Clearly, when people work long hours, there is a greater tendency to come in early and do their work before the start of the official work day. The chart below show the percent of time spent during each of the 24-hour periods of the day, starting at midnight, the “0” hour.

(On the chart, it appears as if work drop off in the afternoon. This is because some  employees shift their hours by arriving very early in the morning and finish their day by 3:00 p.m. or 4:00 p.m. )

What does this mean for organizations? If they plan to provide snacks to those who work overtime, breakfast items may be more appropriate than dinner items. And if extra meetings need to be scheduled, employees may be more willing to come in early than to stay late. Finally, energy levels may be higher in the morning than at the end of a day when some employees have already worked ten hours or more.

Undestand the hours of work when you are most productive. Your time is worth it!

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Mark Ellwood is president of Pace Productivity, an international consulting firm that specializes in improving corporate productivity. His passionate mission is to improve people and processes through consulting and training.