There is a problem … what do I call modern architecture? Perhaps the obvious answer is to just call modern architecture modern but then design historians talk about Post-Modern architecture from the 1980s and early 1990s so surely anything more recent has to be post post modern? Or is that just trying to be too rational?
For me I couldn't possibly be old fashioned so one way of looking at this is to say that anything that was designed since I was 15 is modern. But then my modern can't be your modern unless you were 15 when I was 15 which is possible but a bit of a coincidence.
Why 15? Well that's roughly the age when adolescents seem to have developed both a more realistic sense of time and history and an interest in fashion and a sense of a personal style … before that it tends to be just wanting exactly the same things as everyone else in their class at school.