Been months since I did this. And it's pretty useful, especially to me, because I never want to miss anything. :D
But here it is, Harry Potter Fests by month, with master lists and posting/prompting/claiming dates included.
January:
hd_erised's 2013
Master Listhd_owlpost's 2013
Master Listmini_fest's 2013
Master Listhrholidays's 2013
Master List
daily_deviant's 2013 Kinky Kristmas
Master List February:
hpsolemnlysworn's 2014
Master List hprare_cliche's 2014 Valentine's Fest
Master Listtorino10154's 2014 Porn Sunday
Master Listdo_me_veela's 2014
Master Listhd_fluff's 2014 Valentine's fest
Master Listhd_remix 2014
Master Listhp_darkarts My Bloody Valentine
Master Listbirdsofshore's HP Character Love Comment Fest
Master List March:
hd_familyfest 2014
Master List hp_getlucky 2014
Master Listhd_hurtfest 2014
Master Listhdotp's Love Meme Comment Fest
Master Listdysfuncentine 2014
Master Listsnarryglompfest 2014 Snarry Glomp Fest
Master Listrhrsmut 2014 Ron & Hermione Smut Fest
Master Listblack_circle_dj 2014 Remus/Sirius Fest (final year)
Master List April:
dracotops_harry 2014
Master List hp_darkarts's 2014 Horror Fest
Master Listhp_humpdrabbles's HP Hump Drabbles
Master List May:
hds_beltane 2014
Master Listhp_kinkfest 2014
Master Listharrydracompreg's 2014
Master Listfemmefest's 2014 Femme Fest
Master Listhp_beholder's 2014 HP Beholder (final year)
Master Listgrangerenchant &
gemalfoymanor had a Beltane Drabble War.
June:
hd_smoochfest 2014
Master Listhprarefest 2014
Master Listcapitu's Draco's Birthday Party
Master Listhp_mhealthfest 2014
Master List July:
birdsofshore's Anywhere but the Bed
Master List hpholiday's Fantastic Men (and where to find them)
Master List hp_darkages 2014
Master Listhd_tropes 2014
Master Listsshg_promptfest Severus Snape/Hermione Granger fest
Master Listhp_darkarts Taboo Kink Comment Fest
Master Listhd_cliche 2014
Master List August:
fortheloveofhp Narcissa Malfoy Round
Master Listhh_sugarquill's Houses of Hogwarts Fest
Master Listhrholidays's Harry/Ron Summer of Love
Master Listdm_asp_fest Draco/Albus Love Fest
Master List September:
bbtp_challenge's Bring Back the Porn
Master Listhp_drizzle 2014
Master Listhp_podfic_fest 2014
Master Listhp_silencio 2014
Master Listhd_fan_fair's 2014 Career Fair
Master List October:
samhain_smut 2014
Master Listhp_creatures's Halloween Fest
Master Listhp_laughs's 2014
Master List hp_concrit_fest 2014
Master Listhd_fluff 2014 Halloween Fest
Master List November:
hd_fanart 2014
Master Listserpentinelion's 2014 Glomp Fest
Master Listhp_sexstars 2014
Master Listhp_crossgenfest 2014
Master Listhermione_smut 2014
Master Listinterhouse_fest 2014
Master List December:
hd_erised 2014
Master Listhd_owlpost 2014 Winter Fest
Master Listmini_fest 2014
Master Listhrholidays 2014
Master Listslythindor100's 25 Days of Harry and Draco
Master List. But remember this community has monthly challenges!
daily_deviant Kinky Kristmas 2014
Master List.
And 2015:
harrybang which goes live on Jan. 31st. :)
For Harry/Draco only fests, check
vaysh's awesome list
over here!
I probably missed something, it's really hard not to! But please let me know if I did.
I hope you find this useful though! <3