Jamie seems to have more than one birthday. Paul tells Jamie that something in a dream he had happened on Feb 12, which she says is her birthday. In S05E13 "Astrology," Jamie tells an astrologer that her birthday is Feb 18, but later finds out from her mother that her birthday is actually Feb 19. In S03E24 "Up In Smoke, Part 2," a computer screen shows Jamie's birthday as Nov 11.