Their Zodiac signs? Rory's western Zodiac sign is Libra her Eastern Zodiac (ie. Chinese Zodiac)if your curious is the Rat.
As far as Jess goes his actual birthdate isn't revealed but he is 17 when he comes to Stars Hollow in "Nick & Nora, Sid & Nacy", which is also Rory's first Tag of her Junior Jahr in High School. Since most schools started in September at that time we can assume his birthday is between January and August.
Du could probably narrow down his sign based on his personality traits though.