I remember my grandmother, Karin Nordstrom Hood, telling me a story about Sweden. They used to drive on the left like the British but felt they should join the majority of the world that drove on the right, so they decided to change. My grandma said that the change took three days: on the first day nobody drove, on the second only government vehicles and then on the third day everybody drove. While, I never thought my grandma made this story up (she had been to Sweden after all), it always seemed like such a fantastic story to me, totally unbelievable.
Then today, I saw the tweet pictured above. My grandmother's story, confirmed, totally out of the blue. Although, perhaps the switch did not happen as seamlessly as her story led me to believe.
My mother remembered that this change was reported in the papers, so it must have been a big deal. Since my grandmother had close connections with Sweden, she would have remembered this more than other "big deal" stories of 1967. I just love Twitter, don't you?