Ten years pass between the original Dexter series finale and the events of Dexter: New Blood. The sequel explicitly describes its story as taking place a decade after “Remember the Monsters?”, which originally aired in 2013.
The original finale ends with Dexter Morgan faking his death and abandoning his old identity. After destroying his boat in a hurricane, he is revealed to be alive in Oregon, working as a lumberjack and living alone. New Blood uses that unresolved ending as the starting point for a major time jump.
By the beginning of New Blood, Dexter has moved to the fictional town of Iron Lake in upstate New York. He uses the name Jim Lindsay, works at a wilderness sporting-goods store, and has suppressed his urge to kill for years. His quiet life changes when his estranged son, Harrison, finds him.
The ten-year figure is a story-setting statement, not simply a calculation from the two shows’ broadcast dates. The finale aired in September 2013, while New Blood premiered in November 2021, but the fictional timeline is described as a ten-year gap.