An early point in a real-life process.
Sooner than expected.
Preparedness.
Arriving early for something can represent: the perceived importance of whatever you were early for in the dream; feeling extra-responsible, eager, or impatient about something in your life; a feeling or fear of your timing being off somehow in your life.
For more clues, consider the motivation for and your feelings about the earliness.
See also: Before; Age; Time Frame