How long has megatron been missing from earth?

Megatron has been missing from Earth for a significant period in the Transformers franchise, particularly in the context of the live-action films. In "Transformers: Dark of the Moon," which takes place several years after "Transformers: Revenge of the Fallen," he is absent for about four years. However, in various animated series and comics, the timeline can differ, and his absence may vary depending on the specific continuity being referenced.