April 1917

At first, I thought the letter was dated April 1917.
Then, I realized it was addressed to someone named April 1917.
What kind of last name is 1917?
A trip to the Post Office confirmed their identity and the clerk at Window 3 asked if I had opened the letter.
“Yes,” I said.
“Well, at least you’re honest about that, the clerk said, and a set of tongs held by a pair of thick rubber gloves extended from the wall. “Just place the letter on the tray and we’ll get you decontaminated shortly.”
Damn postman. My name’s 1918, not 1917.