This touches on a sensitive point for many historians, and that is how history is ordered and divided into neat little subcategories, which is also called "periodization". You've got Ancient History, Medieval History, Early Modern History and so on, and often enough a lot of grant money, institutional structure and not least public attention is shaped by those divisions.

Yet here's the problem: All those divions are essentially anachronistic and arbitrary, made up by later historians for a variety of reasons, sometimes propagandistic (the infamous invention of the Middle Ages as a historical term by Italian humanists as a tool to elevate their own time comes to mind), sometimes as simple as "we need to draw the line somewhere". But again, there is no real reason why a man living in 1518's Germany is considered to live in the Early Modern Era, but two years previously his life falls into the domain of medievalists. This can lead to complications because historical subdisciplines tend to work and even think differently, sometimes to an astonishing degree. There is also the added complication that different cultures and historiographical traditions naturally place the emphasis on different topics and points in time. French and German historians often place the end of the Early Modern at 1789, when the French Revolution and the massive chaos and changes it brought drastically altered the face of mainland Europe. But was the UK really that much affected by it? Yes, there was war, but in truth not a whole lot changed for your average Brit in or after 1789. Why not choose the Reform Act of 1832 instead, which represented a massive change in British politics and constitutional history? And what about the rest of the world - why should the Congo, of Japan, or Australia care about arbitrary time divisions thought up by random Europeans?

To be clear: This problem isn't particularly new, and historians have thought a lot during the last couple decades about how to best adress it. The traditional periods are treated ever more loosely, and there is much more cooperation between the subdisciplines now. Looking at the big picture has become almost en vogue, with "long centuries" being a popular research topic now - Eric Hobsbawm established the "long 19th century" for example going from 1789 to 1914, which Iván Berend then let be followed by the "short 20th century" (1914-1989). Those are all legitimate research foci, and weaning yourself from traditional periodizations like the traditional three-age structure of European history or even the number of years in a century can open your eyes to a lot of continuities and changes in history that otherwise might have remained overlooked.

So, to come back to your original question: I'm afraid there isn't any single year you can definitely point at and say that this is where modernity began. As a German historian, the beginning of the Early Modern is traditionally set at 1517 (Martin Luther publishing his 95 theses), but other years like 1455 (used as the year where Gutenberg printed his first Bible, even though he probably did it earlier than that and also printed a ton of other stuff as well) or 1492 (Columbus discovering America) would be legitimate division points as well. Many historians would say that there is a big change in history going on during the 15th and 16th centuries, and to be honest the discovery of the Americas really was a huge change, but ultimately you can't pinpoint a single year, and neither can you really be sure that this "age of change" isn't just something that came up because we have the benefit of hindsight.