There are 50th birthdays and 50th birthdays.

I had my big day last year -- the day when life flashes to another color -- and my husband was to have his this summer. My friends and I are all rounding the big corner these days. With stabbing fears that we are metamorphosing into people we don't recognize, or toting lives that lack any scrap of luster, we're grappling, swapping skins, trying to find the new garb or lifestyle or vehicle that will both free and armor us for the years ahead.

It's no longer the runaway truck that we fear, but something more lurking, intentional and inevitable. And no matter how bright we try to be, we all look a little wan or frayed around the edges. There's a telltale bruise on the calf or deep-dwelling in the eye. Bravely, we all try to celebrate -- or forget -- the big day in some significant way or another.

My friends and I have celebrated our 50 years of life in a variety of ways. I took a trip to see old friends from youth and childhood -- two friends, now living in New York, from schools I attended in Japan, and another from graduate school days in Cambridge. A friend invited a motley assortment of 10 of her close friends to a beach house in Maine, where they lived it up, scrambling on rocks and drinking sangria. Another went to the Boston Museum of Fine Arts with her kids, and finished off with a delicious pizza -- "Double the olive oil, please!" -- in the North End. Another traveled to a hotel in Salzburg, where she had been billeted with her colonel father as a girl, and sat overlooking the Salzburg rooftops, sipping Diet Coke and munching chocolates, surrounded by the flowers her friends had ordered ahead.

Then there are the men friends. One took a trip to Australia, and dined with his wife in Perth. Another bought himself a Hinckley yacht. Two others -- lacking imagination -- had boilerplate celebrations: The first, fantasies of orgies with scores of beautiful women swirling in his head, divorced his wife and took up with his hairdresser. The second, sensing the sickle grazing his heels, purchased the red BMW convertible.

Other friends, less lucky -- the ones with cancer, brain tumors or MS -- have brought in the next decade, breathless, just relieved to be alive. Able not only to smell roses, but to really taste the cream in a chunk of brie, and sense the tingle of their children's laughter penetrating their skins -- they may be the happiest of us all.

Now it was my husband's turn.

As the end of June -- and the fateful day -- neared, my previously happy-go-lucky husband was looking a little green around the gills. I worried: Would I ever see his easy smile again?

And what would be the perfect gift to celebrate this day? Peter's the sort of guy who still, at his advanced age, works a job to try to save the world, sinks into bed with a sailing adventure book every night, and follows minute to minute the twists and turns of the Tour de France. He's a guy with few wants, so I puzzled and puzzled over what to get him.

As it turned out, my husband wound up in Geneva, on a business trip, on his birthday. My children and I, envious of his chance to watch tour boats glide across Lac Leman in the twinkle of dusk and feast on Lindt chocolate and fondue, scoffed at his self-pitying phone calls across the Atlantic. To his protests that he was spending all his time in meetings, locked into a canned-air hotel, and that he wanted to be with us, we replied, "But you're in Europe!"

When he got home -- 50 years and five days old -- we received him with a shortbread-crusted fruit tart, new shirts in spring green and violet, a navy-and-purple-striped tie, and two books on sailing around the world. I even made him a 1968-style hippie love bracelet out of rawhide. He seemed happy, but his smile was wistful . . .

The next weekend, we threw him a party -- two more cakes: lemon and chocolate chip, and an evening with lovely friends under the maple in the back yard -- but still, to paraphrase Miss Clavell, "Something was not right."

The day after the second party, we happened to be in a hardware store, buying a can of paint, when suddenly my husband sidled up beside me with a smile to beat the band. He and our son, Forrest, had gone next door to check out the bike shop behind the hardware store.

"There's a bike next door I want to buy for Forrest," he said.

"Forrest already has a bike," I said. But sensitive to the newborn tremble in my husband's strong, 6-2 frame, and curious about the lighthouse beam of happiness suddenly raying from his face, I humored him, rolling my eyes at my daughter. "Okay. Let's see this thing."

Minutes later, we were standing beside Bob, the bike shop owner -- a naval mechanic who'd retired (heading toward 50) by buying this little, messy bike shop at the back end of town -- looking at: not the fancy, graphite-framed, drop-handlebarred 21-speed with Dura-Ace components and brake-handle shifters that I knew my son would want, but at a bike that barely reached as high as my thigh. My husband's hand was resting on a spanking new, shiny-black, one-speed Stingray, with metal-flake finish, banana seat and chrome sissy bar, and his smile was a thousand watts. So this was what my husband wanted!

Bob was standing right there beside my husband, with nary a hint of a grin on his face. He understood, to the depths of his boy soul, the importance of this classic 1960s American icon.

A knees-in-the-chin test ride and $120 later, Bob was helping us load the black devil into the trunk with the paint, the new sponge mop and the groceries.

On the way home, Peter allowed as how his three brothers had all had Stingrays when he was a kid, but he'd always had to beg a ride on Jamie's. As he swung the car easy along the curves of the back road, deft as Lance on Mont Ventoux, I could see that something was now righted in the world.

So far, no trophy blonde or escape trip around the Horn. But life has changed since my husband and I made the big turn: Now we drink lemonade and eat snow peas in the back yard and then we go pop wheelies in the front. With a crowd of other fifty-something neighbors around us, clamoring for a turn.