"Everyone knows" is among the most unqualified justifications that people can come up with.Everyone knows that the older generation is wiser and more moral, and younger generation just gets worse. Don't believe? Just ask any uncle or auntie.
Let me boorow a few lines from Baz Luhrman's "Sunscreen" (it actually comes from Mary Schmich of Chicago Tribune):
How old are you?Accept certain inalienable truths, prices will rise, politicians will Philander, you too will get old, and when you do you'll fantasize that when you were young prices were reasonable, politicians were noble and children respected their elders.
You are clearly falling for the illusion that just because something creates more noise in the news it means is has not happened before.
An example: premarital sex. Today we know it happens, only really blindfolded people will dispute it. But what about earlier days? You will be the first one denying that it happened during the age of your parents, given your above response.
An official from Bavarian administration (similar to Singapore Registry of Marriage) simply compared the date of birth of the children with the marriage date of the parents. It should give at least 8 months, right (allowing for some fluctuations, early delivery etc). He got an average of 5 months. That was around 1910.