“How can we prove the Messianic kingdom was set up in heaven in 1914?”
They used to use a mathematical formula from 607BCE. You remember, time ,times ,and half a time, and all that.. I have not heard that for years , apart from my diehard old relatives who still remember it. Nowadays they just use observation and some quotes from certain writers. They list World Wars global warming etc as proof that this is the time of the end.