Time flows differently in all five worlds so for convenience time is usually measured by how long it has been on Earth.
But just so you know...
1 Earth Day = 1 Heaven Year
1 Earth Year = 1 Spirit Day
1 Earth Second = 100 Hell Years
1 Earth Minute = 1 Reflected Hour
(Reflected time how that flow of time in the Mirror World.)
Fastest to slowest:
-Underworld
-Heaven
-Mirror World
-Earth
-Spirit world