How we describe time directly affects how long we perceive it to last, and that effect extends to deadlines, motivation and decisions — even when the same time period is involved. This is the conclusion reached by Deepak Sirwani, an associate professor at the Sauder School of Business at the University of British Columbia, and the research was published in the Journal of Marketing Research.
For example, if a person is reminded that only three months remain until the end of the year, they may feel an urgent need to act. But the phrasing "two months and 17 days" may produce a lesser sense of urgency, even though in reality less time remains.
The researcher studied how the presentation of time intervals affects their subjective duration. Across ten studies — including an analysis of more than 10,000 online course listings and nine experiments involving more than 6,000 people — a pattern emerged: a time period seems longer when it is described using both large and small units at once.
Thus, "two hours 55 minutes" may be perceived as a longer period than "three hours," even though the second interval is five minutes longer. According to Sirwani's explanation, upon hearing "three hours," a person mentally operates with large units of time, whereas mentioning minutes shifts attention to smaller segments, which makes the total time seem longer.
This effect can influence goal-setting and everyday decisions. For example, in one experiment, participants chose less ambitious weekly physical activity goals when workout duration was stated in hours and minutes rather than rounded to whole hours. The same workload seemed more significant in the first case.
In everyday documents, advertisements and contracts, deadlines are often written in the first form that comes to mind, without considering how it will be perceived. This is one of those cases where word choice can change a person's behavior, even when the numbers stay the same.
For example, an online course listing that says "three months" and one that says "two months and 25 days" may receive different responses, even though they refer to the same deadline. The same applies to product shelf life: an exact date on the packaging may prompt a consumer to discard the product sooner than a mention of the month alone.
The author of the research himself notes that there is no universal formula — everything depends on what behavior you want to encourage. But it is precisely that flexibility that makes this knowledge practically useful, both in marketing and in public communication.
