Until the 19th century, the birth of Jesus was nothing more than a strictly religious holiday. Two centuries ago, the industrial revolution brought mass production, the still lasting exponential growth of wealth, health, population, and standards.
The regime change in the former Eastern Bloc may rarely be connected to one specific date. It is rather considered a process which took place between 1989 and 1990. Of course,there were several important events. But none of them could be identified solely as “the” one that signifies the change of a regime.