It didn't. Jesus rode into Jerusalem on Palm Sunday.
Palm Sunday
No. Palm Sunday now commemorates that day.
Palm Sunday became important when Jesus triumphantly into Jerusalem.
Palm Sunday is when Jesus rode into Jerusalem on a donkey.
palm Sunday is all about how that when Jesus road into Galilee and his worshipers threw palms at him --another answer-- Palm Sunday (not Psalm Sunday) is about the entry of Jesus into Jerusalem, when people laid palm branches on the ground as he approached. This was a sign of honour in those days.
Palm Sunday is when we celebrate Jesus' triumphant entry into Jerusalem for Passover. We call it Palm Sunday because, while Jesus was riding the donkey into the city, his followers were waving palm branches and shouting "Hosanna, blessed be the King!"
Palm Sunday
According to interpretations and Sunday school studies, on the Tuesday after Palm Sunday Jesus provided more lessons, such as that of the fig tree. He preached in Jerusalem.
Palm Sunday was Jesus' triumphal entry. People laid their clothes and palm branches on the road that Jesus came into the city with. So as tradition a lot of churches hand out palm branches as a remembrance.
Jesus clensed the temple and came on a colt on Palm Sunday.
It is a Palm Sunday as it called by now by the Catholics.