Then there are important events that we know happened. You have all kinds of memories stored in the computer known as the human brain. They come from everywhere. Parents, peers, teachers, friends, wise old men and women. Books, newspapers, television, CD's, DVD's, rumors, theories, gossip.
Most married couples can usually remember their first date.
They may recall it differently, one dreaming of what they did, another of where they went. They may not agree on what they wore, or whether they had fun, or talked or sulked, or even argued. But they will remember the event, even if the day of the week, exact month or year escapes them. My first date with the girl who was to become my wife was April 25th. Easter Sunday that year.