Perjury is more than just saying something factually wrong on the stand. Republicans spent years talking about how getting trump in a courtroom was a perjury trap because he would make a small mistake like recall the January 12 of 2011 was a Saturday and then they prosecution would be like, “no it wasn’t and now you go to jail because we hate America”. In reality, perjury basically takes someone knowingly and intentionally entering testimony that is false. Simply forgetting that he wasn’t president at the time would not qualify.