In temporal logic, calculational proofs beyond simple cases are often seen as challenging. The situation is reversed by making temporal logic calculational, yielding shorter and clearer proofs than traditional ones, and serving as a (mental) tool for unification and discovery. A side-effect of unifying theories is easier access by practicians. The starting point is a simple generic (software tool independent) Functional Temporal Calculus (FTC). Specific temporal logics are then captured via endosemantic functions. This concept reflects tacit conventions throughout mathematics and, once identified, is general and useful. FTC also yields a reasoning style that helps discovering theorems by calculation rather than just proving given facts. This is illustrated by deriving various theorems, most related to liveness issues in TLA+, and finding strengthenings of known results. Educational issues are addressed in passing.