Jet lag is a temporary mismatch between your body’s circadian rhythm and a new local day–night cycle after crossing several time zones. The CDC notes that it most often follows travel across more than three time zones and can affect mood, concentration, and performance.
To reduce it, begin shifting sleep earlier (eastbound) or later (westbound) a few days before departure, then follow destination meal and sleep times once you arrive. Favor daytime light at the destination, drink water, avoid alcohol, use caffeine only earlier in the local day, and keep daytime naps short (about 15–20 minutes) so nighttime sleep stays possible.
Source: Jet Lag — CDC Travelers’ Health