Conformally invariant proper time with general non-metricity Adrià Delhom, Iarley P. Lobo, Gonzalo J. Olmo and Carlos Romero Eur. Phys. J. C, 80 5 (2020) 415 Published online: 12 May 2020 DOI: 10.1140/epjc/s10052-020-7974-y