One little usability bit that I picked up from many of the Web 2.0 apps (in particular 37signals apps), is displaying date and times in a “how long since” format.

Take a look at the community page on Silver Arcade. I wanted to display when a user became a member of the community. Instead of displaying the actual date that they signed up, I choose to convert that date to “how long ago”.

At first I did this just because I liked it. Then it began to dawn on me that there are reasons that I like it.

Questions

One primary purpose of any UI is answering the user’s questions. “How much credit is left in this account?” “Is this customer currently active?” “How many days are left before this explodes?”

Frequently, when we are displaying dates and times we are really trying to answer questions that begin with “how long ago did …” or “how soon until …”.

When we display a simple date and time, such as  “August 22, 2009 12:11 PM”, we are providing raw data to the user, but we really aren’t answering their question. We’re leaving the final step up to them. That’s translating that raw data into a meaningful answer for their ‘how long’ question. Every translation has a cognitive cost.

This may not seem like much, but the cognitive cost adds up very quickly. This can be one of those subtle points that makes two seemingly similar interfaces feel so different.

I’m not saying to display every date and time in your application in this format. Instead I am saying to ask “what question will my users have and am I really answering it”.

To be fair, this is purely anecdotal and is not backed up with any empirical evidence.