forty-two years later

I rang my father just now and he said he was just about to crack open a bottle of champagne with my mum. I wondered why.
"Elfter neunter," he explained in German.
"9/11?" I said, completely confused as to why they would be celebrating September 11.
"Our wedding anniversary," he reminded me. Geez, what a day to have it on.
Wow. 42 years. Congratulations, Oma and Opa.