It is in the bible, and Jesus Christ created it. Perhaps you better read the OT a little closer. It was impossible to celebrate before Jesus arose from the dead, so it was alluded to by the prophets. Let us know when you know where it's found.
There is no mention of anyone in bible observing "Easter", even up to 60 something years after the death of Christ. There is no doubt that the resurrection of Christ is in the bible. But God commanded, Jesus Christ commmanded, that we observe his death, at Passover, a God created day:
1Co 11:24 And when he had given thanks, he broke it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
1Co 11:25 After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
1Co 11:26 For as often as ye eat this bread, and drink this cup, ye do show the Lord's death till he come.
This is of course why the Lord created Passover and commanded his followers to observe it, to show the Lord's death until he shall come.
Thanks for your kind ping.