Question about Time dilation and space flight?

"Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship's clock (and according to relativity, any human travelling with it) shows... show more "Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship's clock (and according to relativity, any human travelling with it) shows less elapsed time than the clocks of observers on Earth. For sufficiently high speeds the effect is dramatic."

So lets assume im travelling at a constant speed and continue doing so for about a year then decide to come back to earth.what speed would i need to achieve to come back to an earth thats aged by say fifty or a hundred years (in the year that i spent away)
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