Time zips by when you're having fun and passes slowly when you're not—except when you are depressed, in which case your time-gauging abilities are pretty accurate. Reporting in PLOS ONE, researchers in England and Ireland asked 39 students—18 with mild depression—to estimate the duration of tones lasting between two and 65 seconds and to produce tones of specified lengths of time. Happier students overestimated intervals by 16 percent and produced tones that were short by 13 percent, compared with depressed students' 3 percent underestimation and 8 percent overproduction. The results suggest that depressive realism, a phenomenon in which depressed people perceive themselves more accurately (and less positively) than typical individuals, may extend to aspects of thought beyond self-perception—in this case, time. They speculate that mindfulness treatments may be effective for depression, partly because they help depressed people focus on the moment, rather than its passing.