Abstract: To transfer a quantity measured in a first unit used by a first entity to a second entity using a second unit, these units being associated with a respective parameter varying as a function of time, the system according to the invention comprises: a means for determining a first operation taking into account variations in the parameter associated with the first unit, in order to convert the latter into a reference unit associated with a constant parameter; a means for applying the first operation to the quantity to be transferred, and for sending the converted quantity to the second system; a means for determining a second operation for converting the reference unit into the second unit, taking into account the variations of the parameter associated with said second unit; and a means for applying the second operation to the quantity in reference units and for transferring the quantity converted in the second system.