Christmas was the Winter Solstice

Easter was Ostara (the Spring Equinox)

Halloween was Samhain

Valentine’s Day was Imbolic

May Day was Beltane

Tuesday was Tyr’s (Tiw’s) Day

Wednesday was Woden’s (Odin’s) Day

Thursday was Thor’s Day

Friday was Freya’s Day

Saturday was Saturn’s Day

Sunday was the sun’s day

7th day sabbatarian’s that argue against Sunday based on Sunday being for sun worship have no basis since Saturday is for the worship of Saturn. It would be more appropriate to instead refer to the days of the week as the 1st, 2nd, 3rd, etc. days of the week. Whether or not one’s weekly day of rest should be on the day we refer to as Sunday or Saturday should not be based on the pagan names of the day of the week since they are all pagan.

While recognizing the pagan influences on culture the Christian should also keep in mind his liberty in Christ and that an “idol is nothing” as Paul wrote in his letter to the Corinthians.

As concerning therefore the eating of those things that are offered in sacrifice unto idols, we know that an idol is nothing in the world, and that there is none other God but one. — 1 Corinthians 8:4

What say I then? that the idol is any thing, or that which is offered in sacrifice to idols is any thing? — 1 Corinthians 10:19

Christians should also remember the numerous commands to learn not the way of the heathen.

Thus saith the LORD, Learn not the way of the heathen, and be not dismayed at the signs of heaven; for the heathen are dismayed at them. — Jeremiah 10:2

An excellent resource regarding paganism’s encroachment into Christianity is The Two Babylon’s by Alexander Hislop.