Early. I thought tôt and de bonne heure Had the same meaning. When do you use each adverb?

I think that, as is often the case; what is the context?

There is strong synonymy between "de bonne heure" and "tôt. However not between tôt and de bonne heure.

Tôt has closer synonymy to "vite" or "rapidement" or "promptement" than to "de bonne heure"

Hope this helps