El Niño, a climate pattern that intensifies across the Pacific Ocean, can slightly slow Earth's rotation, adding about one millisecond to a day's length during strong events. This occurs because El Niño alters global wind patterns: tropical trade winds weaken while west-to-east winds strengthen, redistributing angular momentum between the planet and its atmosphere. The effect is measurable but imperceptible in daily life, as one millisecond is just a tiny fraction of a day's 86,400 seconds. Conversely, La Niña can have the opposite impact, slightly speeding up Earth's rotation and making days marginally shorter. https://www.accuweather.com/en/climate/el-niño-is-making-days-on-earth-slightly-longer/1948550