Traveling east across a time zone means setting your watch forward by about one hour.

The longer version

Earth rotates eastward, so places further east face the Sun earlier and reach noon sooner. Moving east therefore means advancing your watch; each zone crossed adds roughly an hour, and a full circuit of the globe gains a whole day. The effect is continuous in principle but stepped in practice, since clocks jump rather than drift.

That accumulation is exactly what the date line resolves. Without it, a traveller circling the planet would return home a day out of step with everyone else. Airlines print arrival times in local zones for this reason, and passengers often misread a long eastbound flight as being shorter than it was. A westward round trip loses a day overall, which the line restores.

Where this entry sits

These facts wander through clocks, calendars, time zones, and the long human effort to measure passing hours. You will find leap years, odd month lengths, ancient sundials, and the reasons modern timekeeping works the way it does. The full list sits on the Time and Calendars page, where every entry is listed in order.