The Network Calculus theory allows to compute upper bounds on delays and memory usage in data networks. The mathematical foundations rely on piecewise-continuous functions being, depending on the authors, either left-or right-continuous. It is then impossible to use all existing results in a single analysis, since the hypotheses are incompatibles. This paper shows how, under some reasonable assumptions, it is possible to project property from left-continuous word to rightcontinuous world, and vice-versa.