Backward jump
From timescalewiki
Let $\mathbb{T}$ be a time scale. The backward jump operator $\rho \colon \mathbb{T}^{\kappa} \rightarrow \mathbb{T}$ is defined by the formula $$\rho(t) = \sup \left\{s \in \mathbb{T} \colon s <t \right\}.$$
