JANUARY
* BATMAN ADVENTURES HOLIDAY SPECIAL #1 is released (in which Harley and Ivy are in a motel room with only one double bed, sparking the first rumours of another level to their relationship) (1995)
* BATMAN ADVENTURES #28 is released (1996)
* 10th-THE LAUGHING FISH premiers (1993)
* 16th - MAD LOVE the episode - premiers! (1999)
* 18th - HARLEY AND IVY - the episode that teamed the gals up for the first time! (1993) 

FEBUARY
* BATGIRL ADVENTURES #1 is released (in which allusions are made to HQ&Ivy's rumoured relationship!)  (1998)
* 1st - THE MAN WHO KILLED BATMAN premiered (1993)
* The month that "MAD LOVE" was published and released!! yay!! (1994) 
* 24th - TWO OF A KIND - Harley makes her debut in the new THE BATMAN animated series (2004)

SPRING
* First ever Elseworld Harley makes her debut in THRILLKILLER '62 oneshot. (1999)

MARCH
* The month that saw the release of "THE DARK KNIGHT RETURNS" - the classic comic in which a futuristic Joker dies. (1986) 

APRIL
* Batman #1 is released - and THE JOKER IS BORN! (1940)
* The long awaited HARLEY AND IVY mini-series is released (2004)

MAY
* BATMAN AND ROBIN ADVENTURES #18 is released (1997)
* Batman debuts in "Detective Comics 27" in "THE CASE OF THE CHEMICAL SYNDICATE" (1939)
* 23rd - Harley's first solo episode - "HARLEQUINADE" (1994) 
* JOKER/MASK Crossover is released (2000)

JUNE
* Poison Ivy is born in "Batman #181" in "BEWARE OF... POISON IVY!" (1966) 

JULY
* BATMAN AND ROBIN ADVNETURES #8 is released (1996)
* 27th - THE VAULT - first episode of THE GOTHAM GIRLS online animated series - debuts (2000)
* BATMAN ADVENTURES #16 - THE BRIDE OF THE JOKER - is released, Ivy crashed HQ&J's wedding and Harley ends their friendship :( (I'm sure it won't last!) (2004)

AUGUST
* "Harley Quinn", the comic that introduces Harley into the mainstream continuity is released! (1999)
* The month that The Haven of Hedonism was officially completed (as it was then) and made known to the world of Bat Fans! (1997) (tee hee!)

SEPTEMBER
* 11th - HARLEY IS BORN! WHOPPEEEEEE!!!!! (1992) 
(Note: This is the day the first ever appearance of Harley in "Joker's Favour" took place, therefore it is generally acknowledged and hailed as her birthday, although her conception and design would've taken place months before)

OCTOBER
* 9th - BIRDS OF PREY liveaction television series premieres (2002)
* 14th - Arleen Sorkin's B-day! YAY! (1956) 
* HARLEY QUINN: THE SERIES makes its debut on comic book stands (2000)
* LAST LAUGH - in which Joker tries to impregnante Harley to carry on his legacy - is released (2001)

NOVEMBER
* BATMAN AND ROBIN ADVENTURES #1 is released (1995)
* 11th- ALMOST GOT 'IM - Harley's second appearance premiers (1992)

DECEMBER
* A "DEATH IN THE FAMILY" runs - where Mistah J murders Robin! (1988)
* NO MAN'S LAND comes to an end with END GAME in which HQ assists Joker with a truly heinous plot to kill hope in the ravaged Gotham City (1999)