This is between the sunsets of Abib the 14th, for Abib 14th (like every day in God's calendar) begins and ends at a sunset.  Thus it begins at sunset at end of Abib 13th and ends at sunset of Abib 14th.
"Oh", does one exclaim, "that is surely Jewish for it commemorates Jewish deliverance from Egypt."  For Jews it commemorates Two Things,--the deliverance from Egypt and then the other deliverance that all men should have.
For all humanity, the universal Contact with God is found in the Passover Lamb, nothing about which is Egyptian.  The slain lamb (in bible religion) ever refers to very God Himself coming in the flesh so men (Jew and Gentile) could lay hold of Him and offer up very God as the once-for-all atoning sacrifice for our sins!
THIS IS WHAT PASSOVER MEMORIALIZES--THE OFFERING UP OF GOD IN INCARNATION FOR THE SINS OF ALL MANKIND!
He was offered up for the sins of all people,--therefore all people should remember Passover!  All Tribes and Races and Tongues are LOST without God!  People of every race and kindred and tongue and  locality are saved if FOLLOWING Jehovah God,--the one and only God there is!
Passover is NOT a Sabbath.  On it, the Passover Lamb was to be slaughtered, at sunset as the 14th Abib came in (at sunset at end of Abib 13th), not one for the nation, but one lamb for every family!  Then it (the hundreds of thousands of them) was (were) to be roasted, and then eaten.  All this butchering, all this roasting, would not be on a Sabbath day.
The Bible does not call it a Sabbath,--not all of the Great Memorial Days are Sabbaths.  Yet, all the world should halt each Passover, to stop, bend the knee, and lift the heart in prayerful praise and worship for very God Himself coming and being offered up for the sins of us all, for all humanity!
Take the Lord's Supper at this time, for now the elements that memorialize the sacrifice of very God He Himself has designated as the fruit of the vine and the unleavened bread.