The federal retirement system certainly encourages people to think about their careers in terms of chronological age. Once you hit a certain age with a certain number of years of service, you are eligible to retire, either under standard policies or under early retirement authority, if available.

But the difference between the current year and the year listed on your birth certificate increasingly is an outdated way of thinking about a working career. What matters more these days is “career age” and that may have only a loose correlation to chronological age.

That’s become clear in recent years as many people—not just federal workers—delayed retirement beyond when they had expected to leave the workforce. In many cases, it was because of financial losses or uncertainty. In other cases, it was the related factor of outside work prospects—for those thinking of continuing to work, at least part-time, after retiring from the government.

One thing that both chronological age and career age have in common is that people are passing milestones later than they did in prior generations, said a report from the MetLife Mature Market Institute. For example, 50 years ago, two-thirds of people in their twenties were married; now it’s just about a quarter. The median age at first marriage has risen from about 23 for males and 20 for females to about 29 and 27, respectively.

“The pattern is similar for other gateway events, such as the age when formal education ends and the age when transition to retirement begins,” it said.

On that score, “career age” is a measure based not so much on years but on acquisition of knowledge and skills. While in the past it was the rule that a person tended to stick with an occupation for an entire career, that is no longer the case, and older people who have switched careers may “consider themselves to be in an early-career stage even though they bring extensive work experience to their jobs.”

For example, in a recent survey of workers age 50 and up, 42 percent said they were mid-career, and several percent considered themselves early in their careers.

For the employees, there is the risk that the employer will consider them as having one foot out the door based only on chronological age. That would mean being passed by for career developmental opportunities such as training and assignments that would benefit the employee, potentially to include promotion.

For the employer, “old career development paradigms, which assume that workers reach a high level of mastery and then want to coast until they withdraw from the labor force, may be missing important opportunities to engage these employees fully.”

You’ll be doing yourself – and your agency — a big favor by making clear that you are not merely counting down toward retirement.