This is a day Buddhists strive not to sin, to do only good and purify the mind.
This worldview is not understood with ease, being a kind of atheism that rejects the belief of a personal God yet is deeply concerned with maintaining purity with a non-personal Universe. Simply put (as much as one is able), the founder of Buddhism observed a world of suffering and evil under the watch-care of a personal God and he could not reconcile the two in his understanding. Instead, as the celebrants of this day will recall, Gautama Buddha held forth the concept that there is no personal God, that life is full of suffering, so cease craving and suffering will stop. Additionally, one must walk a path of righteousness demonstrated by "right" worldview, desire, speech, behavior, lifestyle, effort, mindset and meditation. The purpose of life is to break the cycle with death following a righteous life. There is nothing beyond the death of a righteous person.
Buddhism is right to take suffering seriously but removing our Creator by preference does not repair the world nor does it repair men--suffering still exists. Men are evil and much suffering is instigated by man. Man cannot repair himself nor is he able to repair others.
Consider at God's unchanging Word: “We fix our eyes not on what is seen [suffering], but on what is unseen [eternal life free of suffering]. For what is seen [suffering] is temporary, but what is unseen [future good life with Christ] is eternal” (2 Corinthians. 4:18, NIV).