in the dispensation of the fullness of time, so as to renew in Christ everything that exists through him in heaven and on earth
Other versions
King James Version
That in the dispensation of the fulness of times he might gather together in one all things in Christ, both which are in heaven, and which are on earth; even in him: English Standard Version
as a plan for the fullness of time, to unite all things in him, things in heaven and things on earth.New International Version
to be put into effect when the times will have reached their fulfillment--to bring all things in heaven and on earth together under one head, even Christ.