There's another DC Universe calendar at
http://www.geocities.com/the_time_trust_2000/calendar.htm which draws from the "1976 Super DC Calendar" (check the Neal Adam's art at
http://www.geocities.com/Area51/Corridor/6680/RACDU/DC1976.html There's also notes identifying any discrepancies, plus some additions not covered in the original calendar. Dick Grayson has THREE birthdays listed -- pre-Crisis, post-Crisis and post-Zero Hour!
Interesting point -- Supergirl and Batgirl's birthdays are only one day part -- September 22 and 23. We know that Kara and Babs were close friends, even though they didn't have many published adventures together. But perhaps they celebrated each other's birthday "off-camera", so to speak. Also, this falls exactly on the cusp of Virgo and Libra. I'm no astrologist, but I believe people born at this time share some aspects of either sign. Obviously such birthday placements was a deliberate action, so one wonders which primary characteristic influenced the two heroines -- even though Earth's zodiac would have NO bearing on one born in Argo City, and we don't have their time of birth to do an accurate chart.
Neal Adam's had a lineup of female heroes (Black Canary, Mary Marvel, Supergirl, Lois Lane and Hawkgirl -- WHAT? No WONDER WOMAN?) for the month of September 1976, and it seems that September was an important month for DC ladies. Not only were Supergirl and Batgirl's birthdays in September, but also Huntess Helena Wayne and Flash's wife Iris Allen. Wonder Woman also first arrived on the "Man's World" that month. Other "red letter" days for Supergirl was September 15, when she first met Lena Thorul, and Setember 30, when she was revealed to the world by her cousin.
Hmm... apparently I share a birthday with Sgt. Rock. Anyone also have a birthday with a DC celebrity?