The MAVEN/EUVM solar soft x-ray (SXR) and Lyman-α measurements are compared with analogous measurements made from Earth to characterize the typical error introduced when phase-shifting solar EUV irradiance measurements made from Earth to other points in the solar system according to the 27.27 day synodic solar rotation period. The phase-shifting error, ε, measured at SXR and Lyman-α are extrapolated to the full EUV spectrum by assuming it is proportional to the variability that occurs over the 27-day timescale of solar rotation. Values for ε as a function of wavelength are reported and used to find the typical error for estimates of photoionization frequencies of some major species found in planetary upper atmospheres derived by phase-shifted EUV irradiance. This study finds that the typical extrapolation error for the CO photoionization frequency is 5.7% of the solar cycle mean value, and 87% of the typical 27-day variability.