We hear often about later moms these days, but less about the new later dads who've walked hand and hand with those moms into the modern world of birth timing. While it's always been possible for men to have kids later than women (Sarah was the miracle, not Abraham, when Isaac arrived), the Tony Randalls of this world (new dad at 77) have always been a small contingent.
Like most women, most men tend to have their kids in their 20s and early 30s, though increasing numbers start their families in their late 30s to mid 40s (birthrates to men and women increased in all age ranges between 15 and 45 in the latest data). Though 80% of couples who marry in their 20s have a male partner older than the female partner, and it's not exactly rare to see couples with men a decade or more older, most couples are still within a few years of one another in age (just 60% of couples who marry in their mid to late 30s and over have an older man - much closer to the 50/50 split that would occur if cultural pressure for an older man didn't operate at all).
When birth control gave women the capacity to delay kids until they felt ready for them, whenever that might be, men began delaying at a similar rate, for similar reasons. The new later dads of our moment differ from the later dads of yore in that their wives are their peers - not just close in age, but often with similar educations, job histories and earnings (Ben Affleck  and Jennifer Garner  are one example among millions).
This completely changes the marriage dynamic and has been directly responsible for men's increased involvement in the lives of their kids. If both parents are educated and earning, the logic of separate spheres evaporates. If they're both working outside the home, it only makes sense that they'd share the care work as well. What started within individual marriages has quickly become a culture-wide phenomenon, among parents of all ages.
As men have become more involved in the lives of their kids, they've come to love being there - even as they understand in new ways the time and effort involved in home work. So dads and moms together are forging the movement to innovate new work rules that will allow both members of a parenting couple to be active participants in their families' lives while pursuing fulfilling and decently paid careers ( Families and Work Institute ).
While we're wishing Happy Daddy Day this weekend to all the loving dads, let's take a minute to appreciate how much more involved in the lives of their kids dads are today than when the first father's day was celebrated 101 years ago , and how interconnected are the changing dynamics of dads' and moms' roles inside and outside the home.