A method ascertains a time for a fresh calibration for ascertaining up-to-date calibration parameters of an x-ray device. The x-ray device has multiple degrees of freedom of movement for its recording arrangement. X-ray images of a calibration phantom are recorded for recording positions of the recording arrangement and are evaluated to ascertain the calibration parameters allowing ascertainment of geometry parameters. In multiple operating phases, situated between two calibrations, of a further x-ray device of identical design to the x-ray device, a piece of use information describing the accumulated use of the degrees of freedom of movement during the operating phase and a piece of difference information describing the difference in the calibration parameters between the calibrations delimiting the operating phase, is ascertained and used or determining the time for a fresh calibration.
