I can tell you exactly where I was when President Kennedy was shot — and I have a four-year old daughter. You do the math. If it’s “new” math I can’t help you. I am pre new math. They probably call it something else now.

At 49, I’m not ready to collect social security, but let’s face it, I am an old mom.

It’s not what you’re thinking. I’m not a fearless career woman who wanted to climb the corporate ladder before starting a family. I am not a self-absorbed flake either — I didn’t view motherhood as a trendy, “must-do” experience. No, I just thought mid-30’s was a fine time to start a family. After nearly 10 years of marriage we were ready to balance our lop-sided triangle.

I’m just a girl whose eggs wouldn’t hatch.

I always knew I wanted to be a mom, and I’m not surprised that I’m coming to it late. I am rarely the leader of the pack. I was the last one in my group to get her period, had my first date at 19, ears pierced at 22, first real relationship at 25 and a college graduate at 36. It was destiny that motherhood and middle-age would collide.

On a bad day I’m envious of fresh-faced twenty and thirtysomethings dropping off their preschoolers as they bounce from their SUVs and merrily head to the classroom. Strappy sandals, toe rings and bare midriffs stare at me as my creaky knees struggle to meet Leah at eye level for my goodbye kiss. Occasionally I even feel sorry for myself when I realize that some of my friends are already grandparents. But I have discovered that age can be an advantage in motherhood.

When Leah is a rebellious teen-ager sneaking out of her window in the middle of the night, I will be senile. As she peers over her shoulder with one leg on the windowsill and says “I’m going to the library to study for a test.” I will smile and say “That’s nice, sweetie.”

Retirement comes as our daughter is selecting colleges. With any luck her SAT scores will be higher than our monthly fixed income ensuring financial aid.

Babysitters are plentiful. Our friends and family who pursued a conventional timeline have a ready supply of teenagers to watch our girl. Who better to take care of Leah than her nearly-adult cousins or the offspring of my contemporaries? A babysitter with a mom who is my friend guarantees a no-nonsense evening of care.

I am post-menopausal. By the time my daughter reaches puberty with a surge of hormones controlling her life, mine will be in check. My husband need only survive one estrogen flood at a time in our house.

Skipping generations has its financial rewards too. Leah will save money buying in bulk as my grandchildren and I will be in diapers at the same time.

And we don’t stress about where to vacation like our empty-nested friends. While they spend hours comparing alluring getaways like Rome, St. Thomas, or the wine country, we know we are Southern California-bound. [In our full house, Mickey or Shamu trump anything else the world has to offer. ]

During those uncomfortable moments when someone refers to me as Leah’s grandmother, I lament being an old mom. And I hope that my age does not embarrass her. But I know I would not have been prepared for this experience as a younger woman. There is a reason my daughter came to me at an age when many women are grandmothers and I like to think it’s because I was waiting for her.