Sorry to have missed that. It was in a new topic in a solved one.
When you do:
TDatime T0(2020, 7, 24, 16, 4, 10);
UInt_t X0 = T0.Convert();
X0 contains the encoded date and time. To go back to the initial date you should use GetYear() GetMonth(), etc … all the getters are available. That would be the way to proceed… does it answer your question ?