There's an unassigned issue from 2018 in Emulation Station's bugtracker, but alas, the solution suggested there doesn't work anymore, because the link points to line 256 of https://github.com/RetroPie/EmulationStation/blob/master/es-core/src/components/DateTimeComponent.cpp, but that file has only 129 lines by now, and the original file's line 256 is not part of the current file anymore.
Maybe someone with more programming experience than me can come up with a solution for the current DateTimeComponent.cpp (and maybe post it as another comment in the issue #385).