  In this note, we define the numbers of level crossings by a c{\`a}dl{\`a}g
(RCLL) real function $x: [0,+\infty) \rightarrow R$ and, in analogy to the work
of Bertoin and Yor [BY14] we prove that for $x$ with locally finite total
variation these numbers are densities of relevant occupation measures
associated with $x$. Next, depending on the regularity of $x$ and $f: R
\rightarrow R$, we derive change of variable formulas, which may be seen as
analogous of the It\^o or Tanaka-Meyer formulas. Some of these formulas are
present in [BY14] but we also present some generalizations.
