How long is a day on Umbriel?

About 99.5 Earth hours · orbits Uranus every 4.1 days

The darkest of Uranus's large moons, with one mysterious bright crater at its south pole

Umbriel is the darkest of Uranus's major moons, but has one mysterious bright feature called Wunda - a 140km crater near its south pole that shines like a beacon on an otherwise dark world!