Historic periods rarely have well-defined dates, unless they can point to a specific event that created definitive change. One can say there's an "Atomic Age" that started with the dropping of the bomb on Hiroshima, for instance. Human history is divided into three periods: Classical Antiquity, The Middle Ages, and Modern History. There is, of course, "pre-history" where we have evidence of human beings but no written records (we are ignoring cave paintings).
The Middle Ages itself spans such a long time that it is convenient to split it into Early (late 5th century to 10th century), High (1000 CE to 1300s), and Late Middle Ages (about 1250 CE to 1500). You can't help noticing that High and Late overlap by at least 100 years.
For me, the Middle Ages ends in 1453. That year is not quite as arbitrary as the "official" year of 1500, picked (I assume) because it was a nice round number. I like 1453 because there are events—two specific and one approximate—that make large enough changes politically and culturally that it seems to me things in Europe will never be the same.
The first is the final end of the Hundred Years War. The economies and cultures of England and France were dominant through much of the previous centuries; their political alliances and hostilities affected several other countries, their trade partners as well helped create a "global" economy. With the French victory at the Battle of Castillon in 1453, a long period of instability that had started in 1066 came to and end. (Yes, there were military conflicts between France and Great Britain afterward, but no large or sustained campaigns. They are sometimes referred to as "The Second Hundred Years War." In fact, there was a period of 1159-1259 referred to as "The First Hundred Years War." [sigh])
The second specific event is the final Fall of Constantinople. (I feel obligated to designate it "final" because of the disastrous Fourth Crusade, which for some reason I have avoided discussing. Some day...) The result of a 53-day siege by the Ottoman Empire, it not only altered the history of one of the constants of history—Constantinople had never lost its reputation the way Rome did after the Goths—but it also marked a change in siege warfare. Until then, strong walls/ramparts had prove effective against siege warfare, and Constantinople had very strong ramparts. They were defeated, however, by the use of gunpowder. Defeating a well-defended city became easier. Constantinople became the new capital of the empire. There was a secondary result of this conquest: an influx of new (and classical) learning through Greek texts brought to Western Europe by scholar fleeing Constantinople. The Renaissance had already started in Italy and elsewhere, and now would be enhanced by the new scholars and scholarship.
My third (and the "approximate" event) was a development brought about by a German named Johannes Gensfleisch, whose expertise with metal work helped him perfect a process that had actually been around for 200 years—just not in Europe. We know him now as Johannes Gutenberg. The famous Gutenberg Bible took about two years to set and print, and was completed in 1454. We are certain his press was in operation as early as 1450. The cultural sea-change brought about by the relatively easy method of providing the world with books without fear of scribal errors cannot be calculated. There were fears that learning would not be appreciated properly or used wisely—once you let just anyone have a book, the less-educated could misinterpret it and spread misinformation. It is likely that an elite class would oppose widespread dissemination of learning in order to maintain their elite status (which is why movable type did not become widespread two centuries earlier). The cat was out of the bag, however. It is likely that the choice of printing an impressive Bible helped some see the beauty and utility of mass-produced books.
...and that, for me, is why post-1453 would never be the same in Europe and the very-near East. Now, as much as I want to talk about that "First" Hundred Years War, you may be sick of that topic and the petty fighting between England and France. For a change, let's look at the "failure" of movable type to catch on in the 13th century, and for that we have to turn to a country never before mentioned in this blog: Korea.