Planet Earth was formed 4.6 billion years ago. And while the interpretation of the earliest fossils of life is debatable, we can say that some 3.6 billion years old remains probably are fossils of bacteria.
But right after the formation, the surface was still molten lava, and there was heavy meteorite bombardment [1]. So from the time the planet had cooled down, and the solar system had calmed down, to the beginning of life (which could have happened earlier than there are fossils left) could have been anything from mere 100 million years to over 600 million years, for all we know.
