Authored by Ross Pomeroy via RealClear Science (emphasis ours),
It seems a tad odd, but it's also true: Take a look at advertisements for traditional watches (you know, the ones with the rotating 'hands'), and you'll quickly notice that the time on the watches is almost always set to 10:10. This has actually been the norm since the 1950s, but why?
A simple explanation is that this setting keeps the hands out of the way of the watch's brand, so 'Rolex' or 'Cartier' can be placed front and center, but other time settings also accomplish this aim. A different explanation might prompt surprise and understandable skepticism: 10:10 sells more watches because the arrangement of the hands subtly resembles a smile, thus leaving onlookers in a better mood.
An international team of researchers explored the latter theory in 2017, publishing their results in the journal Frontiers in Psychology. They recruited 46 participants to look at sixty pictures of various watches with their times either set at 10:10, 11:30, or 8:20, asking participants to rate both their emotional response to seeing each picture as well as their likelihood to buy each watch. Subjects rated watches set at 10:10 as slightly more pleasurable compared to watches set to the other times. They also said they would be slightly more likely to buy them.
In a second experiment, the researchers recruited twenty more subjects to each view twelve different images in random order of watches again set at 10:10, 11:30, or 8:20 and rate how much each setting resembled a picture of a smiling or sad face on a scale of one to ten. Overwhelmingly, subjects said that watches set at 10:10 most closely resembled a smiling face while watches set at 8:20 most closely resembled a sad face.
While the research could have benefited from a larger sample size, particularly for the first experiment, and probably should have compared more time settings, it did decidedly support the hypothesis. Marketers are well known for exploiting any angle they can to sell products, and setting clock hands on traditional watches to 10:10 does indeed seem to subtly influence prospective purchasers.
Source: Karim AA, Lützenkirchen B, Khedr E and Khalil R (2017) Why Is 10 Past 10 the Default Setting for Clocks and Watches in Advertisements? A Psychological Experiment. Front. Psychol. 8:1410. doi: 10.3389/fpsyg.2017.01410