Hi. This might be also a matter of opinion, but if we consider single days of history, which are often considered as most remarkable in human history? Like top 5?
There are many ways on how a most remarkable day in history could be defined, depending on your perspective. One possibility would be to list 5 specific days in history where specific events occurred that had the highest possible impact on the highest number of people . An example of such a list would be as follows:

1. 12 October, 1492: Columbus reaches America, beginning a new era for Europe for exploration and colonization which would eventually expand to the entire world.
2. 14 July, 1789: French revolutionaries seize control of the Bastille, the culmination of events that followed afterwards would lead to the end of the Ancient Régime, the central power structure that had ruled Europe the centuries prior
3. 28 September, 1928: The discovery of Penicillin the first effective antibiotic, by Alexander Fleming which revolutionized medicine forever.
4. 16 July, 1945: The denotation of the first nuclear weapon "Trinity", marking a new era in warfare where any direct conflict between nuclear powers will lead to mutual destruction.
5. 29 October 1969: The first message sent from computer to computer through ARPANET, the beginning of a new era of instantaneous communication