Actually, this is not backed up by the scriptures. Christ's followers were commanded to keep the anniversary of his death, which this year falls on the 11th of April. (a Tuesday) This corresponds with the date of the Jewish calendar month of Nisan, on the 14th day. This is also the same date as the Jewish Passover because it was held on the same night. Christ is the Passover Lamb....his blood saves those who put faith in its value.
There is no command to commemorate Christ's resurrection, even though it was a prophesied event. It was the blood of Jesus shed on Nisan 14 that paid for the sins of mankind. (1 John 1:7; Hebrews 9:13-14)
Revelation 1:5:
"from Jesus Christ, “the Faithful Witness,” “the firstborn from the dead,” and “the Ruler of the kings of the earth.”
To him who loves us and who set us free from our sins by means of his own blood."
There is also no Biblical record of Jesus being put to death on a cross. The Romans had various configurations of their instruments of torture. But the one used for Jesus is described as a "stauros" which primarily denotes an upright stake, or pole, and there is no evidence that the writers of the Christian Greek Scriptures used it to designate a stake with a crossbeam.
The book The Non-Christian Cross, by John Denham Parsons, states:
“There is not a single sentence in any of the numerous writings forming the New Testament, which, in the original Greek, bears even indirect evidence to the effect that the stauros used in the case of Jesus was other than an ordinary stauros; much less to the effect that it consisted, not of one piece of timber, but of two pieces nailed together in the form of a cross. . . . it is not a little misleading upon the part of our teachers to translate the word stauros as ‘cross’ when rendering the Greek documents of the Church into our native tongue, and to support that action by putting ‘cross’ in our lexicons as the meaning of stauros without carefully explaining that that was at any rate not the primary meaning of the word in the days of the Apostles, did not become its primary signification till long afterwards, and became so then, if at all, only because, despite the absence of corroborative evidence, it was for some reason or other assumed that the particular stauros upon which Jesus was executed had that particular shape.”—London, 1896
The cross as a religious symbol predates Christianity by centuries....and it has very unsavory roots.