I did 7-minute ab wheel planks every day for a week — here’s what happened to my body . With the form nailed, I decided to add the core-focused exercise to my daily routine for a week.

Days, months, and years all make sense as units of time—they match up, at least roughly, with the revolutions of Earth, the moon, and the sun. Weeks, however, are much weirder and clunkier. A ...

Why are there seven days in the week? No, this isn’t a question that a curious 10-year old asked me. Instead it was the late-night group musing on a recent work trip. After an extended back and ...