Time translation symmetry
From DispersiveWiki
A PDE is said to have time translation symmetry if for any solution u(t,x) the function u(t + t0,x) is also a solution for all (or some interval of)
. Generally speaking, a PDE has time translation symmetry when the coefficients and data do not explicitly involve the time variable t.
A PDE which has time-translation symmetry is also called time-translation invariant or autonomous.
One can often use time-translation symmetry to bootstrap a local well-posedness result into a global well-posedness one, provided that one has some uniform control on the lifespan of the solution provided by the local well-posedness theory.

