It's happened twice in the last few months in two stores in my West Village neighborhood.

Cashiers at a national grocery store and at a pharmacy chain asked me for identification when I was buying a six-pack of beer. Me? I was in high school when JFK was shot, and went to Woodstock in 1969.

Give me a break!

"What?" I asked, taking out my senior citizen MetroCard, which includes my photo.

Both cashiers refused to accept the card as proof of age because it does not list my date of birth. (Like many New Yorkers, I don't own a car and don't take my driver's license on local errands.)

"Why do you need a date of birth if it says I'm a senior citizen?" I asked, drawing an angry look. "I'm obviously over 21. And you must prove your age to get a senior MetroCard card."

Both cashiers responded like programmed robots, going on about needing a date of birth. I had to call for the manager in the pharmacy to buy my beer.

I apologized to all the customers behind me for holding up the line.

But I was more surprised at the interrogation I was subjected to at the grocery store -- a new cashier -- because it's the corner store where I shop often. I also made a little scene in the supermarket to buy the beer.

According to the New York State Liquor Authority, acceptable identification includes a valid driver's license or other state-issued ID, a passport or military identification.

Because 13.5 percent of the New York City population is age 65 and older -- and that number is climbing -- I suggest the senior citizen MetroCard be added to the list of state-issued identifications. The MTA could start adding the purchaser's date of birth, and that should be sufficient identification.

I understand cashiers in chain stores are trained to follow the law. However, what happened to common sense? Why not require identification only from customers buying alcohol who appear younger than age 21?

One of my college students said she was trained to ask for ID if the person looks younger than 40! (No way I can pass for under 40.) If my 23-year-old niece buys beer, I'd expect her to be carded, but asking 65-year-old me for ID feels like harassment -- and will make me shop elsewhere.

Kate Walter is a freelance writer living in the West Village.