Did you check the link? It’s is fairly clear evidence that the purpose of calender listing is not that the Reformation as a noteworthy historical event, but that it was a righteous confrontation with the “false doctrines” of the Catholic Church. You seem to be confusing recognition of a historic event that impacted society with a fairly blatent example of religious promotion.
Here’s what the link says about the Catholic Church:
“For centuries, the Roman Catholic Church had been plagued by false doctrines, superstition, ignorance, and corruption. Since most ordinary Christians were illiterate and had little knowledge of the Bible, they relied on their clergy for religious instruction and guidance. Tragically however, monks, priests, bishops, and even the popes in Rome taught unbiblical doctrines like purgatory and salvation through good works. Spiritually earnest people tried to justify themselves by charitable works, pilgrimages, and all kinds of religious performances and devotions, but they were left wondering if they had done enough to escape God’s anger and punishment. The truth of the gospel – the good news that God is loving and merciful, that He offers each and every one of us forgiveness and salvation not because of what we do, but because of what Christ has already done for us – was largely forgotten by both clergy and laity. The Holy Spirit used an Augustinian monk and university professor named Martin Luther to restore the gospel to its rightful place as the cornerstone doctrine of Christianity.”
That’s strongly anti-Catholic and in no way a balanced presentation of the “justification” for Reformation; usually fairly characterized in non-religious contexts by the Church’s truly corrupt practice of selling dispensations. The link, instead, presents the basic Protestant fracture from Church teachings; that faith is enough; that that precept comes from the Holy Spirit via the heretic Luther, and that the teachings of the Catholic Church are false.
If that’s not a state-sponsored promotion of Lutherism and protestantism, nothing is. No public institution in the US has any more business linking to blatant denominational promotion, especially one structured at the expense of another faith (Catholicism) as this one is.
The Church in America has enough trouble from its self-inflicted wounds; we needn’t meekly accept more from government institutions promoting anti-Catholic ideas.