Bipolar 2 disorder is characterized by hypomanic episodes lasting about 4 days or less and often includes depressive episodes.

“So BP-II or bipolar disorder 2 is somewhat different than bipolar disorder 1. First of all, it's characterized most often by the presence of both manic episodes, mania, and depressive episodes, or what's referred to as hypomania. Now, anytime in biology or in medicine you hear hypo, it's the opposite of hyper. So we've got normal hyper and hypo. Hypomania is a somewhat suppressed level of mania. So this is not going to be as extreme as the mania that we typically think of. And yet the hypo can be due to the duration, not the intensity of mania. That's right. Hypomania can mean a lessened intensity of mania, but it can also be used to refer to a shorter duration of mania. And in fact, that's one of the key criteria for bipolar 2. Bipolar 2 is often diagnosed on the basis of the presence of manic episodes that are lasting four days or even less.”