If
X(t)---->Time Delay of t - t0---->System----->Z(t) equation 1
X(t)---->System---->Time Delay of t - t0----->Y(t) equation 2
If eq.1 = eq.2 The System is Time-Variant.
If
X(t)---->Time Delay of t - t0---->System----->Z(t) equation 1
X(t)---->System---->Time Delay of t - t0----->Y(t) equation 2
If eq.1 = eq.2 The System is Time-Variant.