The Material Design team published an interesting blog post about the process of designing a 24-hour clock for Android devices
Most of us are probably quite familiar with the classic 12-hour analog clock that once hung in every home (and probably still hangs in many). A simple device equipped only with an hour, minute and possibly seconds hand. It looks similar on smartphones, although this version of the timer needs to have an extra switch to help you determine the time of day when you set the alarm (am/pm). The scheme is quite simple and easy to implement.
Meanwhile, things get complicated when it comes to the 24-hour clock, because how do you put all the numbers you need on the dial? Below, on the left, you can see the first ever Material Design watch that was released in 2020 and consisted of two rings. The larger one, with the characteristic 12-hour arrangement, and the smaller one, which now has the numbers 13 to 24 corresponding to the afternoon hours. On the right you can see another design, this time again with one ring, but only with even numbers. In between, the odd numbers remain invisible. According to Google, thanks to this arrangement, it was possible to eliminate the problems related to the accessibility and contact points of the two rings from the first design.
What are users saying? They didn’t like the new single-dial design because they just had a problem with it – it was hard to figure out how to dial odd numbers at first glance, and they were already used to the double-ring view. Such reception showed that while Google eliminated the problems of the 24-hour clock, it did not live up to the expectations of Android users. As stated in the blog:
While the updated design solved key accessibility issues, there was still a disconnect between users’ mental models and the new 24-hour analog dial.
So we set out again to find a suitable solution. One and two ring designs were explored that would satisfy both parties. From the recording we learn that it was necessary to create over 50 unique projects, which were then subjected to a process of elimination, selecting only 4 that met the team’s expectations. So they were made available on a large scale as part of a study to show their utility.
Can we use a 24 hour clock?
The team collected data from more than 50 people in 6 countries (India, Indonesia, Brazil, Germany, France, UK) to obtain user feedback using 12-hour, 24-hour or both models. Among the respondents, it is worth noting, there were also 10% visually impaired people. They were asked to set their clocks to a different time of day in each version and observed how efficiently they performed this process.
It turns out that even those who use 24-hour watches on a daily basis find the designs presented unfamiliar and confusing – it’s just that a similar 24-hour analog watch is so rare that it’s hard to find. It would probably be similar in Poland, because even though we use such a model, we are all used to watches with a 12-hour dial. Regardless of whether it was a one- or two-dial design, there were errors in setting specific times because subjects were not sure how to select a specific time of day.
The conclusion of the study turned out to be really simple – the best solution today is the digital clock, where you only need to indicate which time model is used (12 or 24 hours). Subjects had no problem with it and found it “least confusing”.
However, the Material Design team will continue to research, observing the user experience of using a 24-hour analog clock, to finally offer the most useful, affordable and easy-to-use solution. Is this necessary? Well, that’s another question entirely.