THE POLISHED UP MONSTER HIGH TIMELINE
Note that it's Monster High so naturally a few of these placements may contradict each other. Friday Night Frights could go after Skull Shores, but there's more evidence to suggest the opposite.
Also webisodes are evidently not in chronological order all the time, which is why not only can certain webisodes from certain volumes bleed out across the timeline, but also why I made the placement of the volumes so vague ( ie " the Volume 6 webisodes would happen near / around the end " rather than EXACTLY at the end ).
The video game New Ghoul In School likely takes place the following school year ( September 2014 )
Writing out the timeline displayed:
September 2011 - June 2012: New Ghoul At School + All of Volume One
September 2012 - December 2012: Fright On, ( Most Likely ) Friday Night Frights, Ghouls Rule. Volume 2 Webisodes mixed with a few Volume 3 Webisodes
January 2013 - Mid March 2013: Ghoulfriends Forever starts, Why Do Ghouls Fall In Love, Ghoulfriends Forever ends, Scaris City of Frights, Escape From Skull Shores. Volume 3 webisodes
Late March 2013 - June 2013: Ghoulfriends Just Wanna Have Fun, Who's That Ghoulfriend, and Til The End. It is possible for Ghoul It Yourself's mini story to have started in the summer break. Volume 3 Webisodes.
September 2013 - December 2013: 13 Wishes, Frights Camera Action. Volume 4 Webisodes + a few V3 Webisodes
January 2014 - Mid March 2014: Freaky Fusion, Ghoul it Yourself could have possibly also happened between This and Haunted, Haunted. Volume 4 and a few Volume 5 webisodes. Boo York could very well be over or close to Spring Break
Late March 2014 - June 2014: The end of Boo York could very well bleed in a little with the beginning of the semester. Great Scarrier Reef. Volume 6 webisodes with a few V5 webisodes
I will assume that semesters go as follows:
Sept - Dec ( S1 ), Jan - Mid Mar ( S2 ), Late Mar - June ( S3 )
Monster High spans over 2 years and 10 months, that would mean the following characters are, by the end of the series ( some characters are introduced / transfered later in the series ), some characters would, hypothetically, if MH cared about aging:
Clawdeen: 18
Frankie: almost 3 ( mentally likely around 18-19 )
Draculaura: 1602
Lagoona: 18
Cleo: 5845 ( mentally and physically though around the same as the rest of her ghoulfriends )
Abbey: 18
Ghoulia: 18, almost 19
Toralei: 17, almost 18
Purrsephone and Meowlody: 18
Operetta: 18
Howleen: 16
Twyla: 16
Venus: 17
Robecca: 117, almost 118 ( 17-18 yrs )
Rochelle: 417
Wydowna: 17
Jinafire: 1502
Skelita: 16 or 17, up to interpretation
Scarah: 17
Iris: She's slightly confusing as it's unsure if her age ( 15 ) has been established since her first appearance as a background character or since she started developing as a character, however you cannot attend Monster High if you're under 14, so it's safe to assume she's around 17
Catty: 17
Gigi: 16
Jane: 16 or 17
Catrine: 18 or 19, up to interpretation
Deuce: 19
Gil: 18
Heath: 18
Manny: 18
Clawd: 20
Invisi Billy: 17, almost 18
Finnegan: 18
Jackson / Hyde: 18
Nefera: 21
The Undead that aren't proven to age: this is more hypothetical on if these characters could age and what age they would be if possible. Everyone has their own Headcanons though:
Spectra: 17.5 ( + 100-200 depending on her death date )
Kiyomi: 16 or 17, depends on interpretation
River: 13, 14, or 15 depending on interpretation
Slo Mo: 20
Johnny: 15-18
Any characters not included is likely because of how new they were in G1 and likely wouldn't have aged much, or they just didn't age much period.
REMINDER
Monster High is known for anything BUT it's continuity. There could be lore explanations for why some characters are in Monster High despite being too old, and sometimes ages are likely forgotten by creators which happens a lot.
My math is also not the best so please feel free to correct me.
There are also issues with monsters who apparently age differently ( Rochelle, Robecca, Jinafire.. ) or age in " Monster years " ( which was never explained ). To that I say: make up how it works. Maybe Robecca gets rebuilt / remodeled to fit her new age, maybe gargoyles and dragons age in a gradient rather than a linear pattern, maybe some monsters need to form a connection and then they age, etc..
Or maybe all of Monster High gets the Ash Ketchum treatment and never age with very little exceptions
Also all of the ages are not canon and are purely hypothetical / what age they WOULD be if Monster High was actually consistent with aging. We do see some characters actually age, so it's really up to Headcanons on whether or not the ages above actually proceed or if they're eternally teenagers thorough out the series
