Exodus 12:11

This is how you are to eat it: with your cloak tucked into your belt, your sandals on your feet and your staff in your hand. Eat it in haste; it is the LORD's Passover.

From the verse above, my guess is like this :
on the day the Israel eat the lamb - it is the day of the Lord's Passover.

Exodus 12:6

Take care of them until the fourteenth day of the month, when all the members of the community of Israel must slaughter them at twilight.

From the verse above, my guess is like this :
The lambs are slaughtered on Nissan 14

Leviticus 23:5

The LORD's Passover begins at twilight on the fourteenth day of the first month.

From the verse above, my guess is like this :
The LORD's Passover day is on Nissan 14

My own conclusion for the time being :
The Lord's Passover is on Nissan 14 - within the same day, some things that happen were [slaughter the lamb, smear the lamb's blood on the door, roast the lamb, eat the lamb with unleavened bread, the dead of the firstborn son]

But that's a non-Christian conclusion. That's why I ask here :
According to Calvinism, what date and what happen during the Lord's Passover in the time of Moses ?

Thank you.