01/27/2013 07:10 am ET Updated Mar 29, 2013

Jon Stewart Is Fifty! Jon Stewart Is Fifty!: What Milestone Birthdays Really Mean

Comedian, satirist and "Daily Show" host Jon Stewart has quizzically remarked several times since Thanksgiving that he is now 50. He says it with what appears to be a combination of amazement, amusement, perplexity and near disbelief. Almost as if, by saying it aloud on a national scale, it will be affirmed or somehow disproven.

He is not alone. About 9 million American baby boomers are becoming 50 or (gasp!) 60 this year. In her recent, Golden Globes award speech, actress Jodie Foster commented "I'm 50! I'm 50! ... You know, I was going to bring my walker tonight but it just didn't go with the cleavage."

Ms. Foster may not have to worry about a walker with or without a secondary use for tennis balls just yet, but there is true value in reflection as we reach a signature age like 50 or 60. Fifty Does Not Go Unnoticed.

wo invitations are inevitable at 50. There is that ubiquitous envelope inviting you to full membership in AARP and a far more disquieting recommendation for a colonoscopy from your physician. And as a special warning to Mr. Stewart, any invitation from the Mets will involve opportunities to purchase a season's ticket, rather than a tryout as a deft middle infielder. When you are 60 the offers for many senior citizen discounts click in.

So what does this mean? Over the past several years I conducted a major study of baby boomers and the things that matter to them for my recent book "Finding Meaning, Facing Fears in the Autumn of Your Years (45-65)."

There are exciting possibilities in being 50. Aging is far more complex than just chronology. Indeed, if you were Chinese, your chronological age would be 51 now. Go figure!
Your chronological age (anniversaries of birth) is easy to calculate, even if the number seems subjectively unreal, but there are other measures of age that may be significant.

Body age, our level of health or physical deterioration, is a strong determiner of lifestyle and capacity of life enjoyment. As a veteran of some painful injuries and conditions, I can attest that being pain-free can be an amazing high.

Psychological Age: how well we have mastered previous developmental challenges is a great indicator of our capacity for freedom and emotional security

Social Age: how well we interact with others in our community and social groups should mature and deepen, as should our personal relationships, particularly long-term ones.

Functional Age: Our capacity or readiness for adapting to new situations, is a measure of how well we respond to what comes our way at home, on the job or in other environs. To what extent can we take the unexpected in stride or to take meaning from it?

Relational Age: At 50 we would expect that a person has carved out a familial relationship that works for her or him. Roles like spouse, single person, parent should suit us.

Reference Age: One of the most interesting questions we asked in our interviews was what age people identified with. Among boomers today, that age was most often in their thirties. So Jon, if you are somehow into the music, feelings and have emotional attachment to the "you" of 15 years ago, you are right in stride with your cohort.

What does 50, 60 or ??? mean?

One thing is sure, if you get caught up in the popular media notions that "50 is the new 30 or 40," or "60 is the new 40 or 50," you will miss out on some exciting possibilities of being your age.

If you are like most of us, a milestone birthday offers opportunities to reflect and explore some important personal questions. Or, to paraphrase that ubiquitous query we make of children and adolescents, "Now that you are all grown up, what do you really want to be?" One aspect of longer life is that we will survive family members, friends and acquaintances. In addition, our physical capabilities, youthful appearance and illusions of invulnerability will fade.

Although these losses may be unwelcome, they do offer us an opportunity to find greater meaning in our lives. Acknowledging that the metaphoric hourglass has been turned over by age 50 and that time, our most precious commodity, is fleeting, may give us the spur to live more consciously, more fully and more in the present.

Indeed, that might be the greatest gift of achieving your fiftieth. After decades of building a future, your milestone age might just be a new chance to live life in the here-and-now and to savor each moment.

So Mr. Stewart, what did you set aside years ago to build your enviable career, that you might want to pick up again? What might be on your bucket list? What joys and pleasures are you putting off that may be more important? What hopes and dreams are best left in the past to allow energy for future growth?

I don't ask these questions frivolously.

I turned 70 this week. And like you, I am a "vertically-challenged," Jewish guy from the East Coast. What is dawning on my consciousness is the semblance of a notion that I will not be getting a call-up from any major league baseball or NBA team, despite the fact that I still have "Stu Miller" speed on my fastball and a well-honed two-handed set shot.

On the other hand I am still doing work I love, having a great birthday week and enjoying being part of the 70+ demographic.

Jerrold Shapiro is professor of counseling psychology at Santa Clara University and author of the new book, "Finding Meaning, Facing Fears, In the Autumn of Your Years (45-65)."

Earlier on Huff/Post50:

25 Celebrities Who Are Aging Gracefully