Each Month begins with a full moon. There are exactly 28 days to each month except for October in which there are 31. There is no moon on the 14th of each month. There are four seasons to each year and each year begins with the beginning of spring when the Nyrundian and Aerdian clerics summon the warm East Winds and break winters hold on Oerth. Monsoons hit the east coasts in spring and the Nyr Dyv begins to flood with the melting snow by the beginning of February. In summer the Red Star appears in the northern skies and is usually thought of as a portent of war. This star disappears from the southern sky by November. The months of August and September contain "Starfall" - a dazzling shower of shooting stars that is sometimes known to interfere with spellcasters. The astrological constellations are also known to have strong effects on the craft of wizardry.
 

January

First month of spring

1st Akitu Festival (11 days), Ceremony to Bring East Winds, beginning of spring
2nd Birthday of Innana-Ishtar
3rd Girru & Gibbil's day
4th Greet Dragon, Epic of Creation
5th Anu temples purified and cleaned, sheep killed to take sins, thrown into river, Rulers take off items of office and claim they have not offended the gods, are slapped by head cleric, Gilgamesh slapped by Archcleric
6th Nusku pyre lit, general sacrificing
7th King drags statue of god around the city for three days by hand,
7th-18th Monsoons hit east coast
8th Officiation by Nabu clerics, dramatic plays of religious epics
9th Day of Anu
11th End of Akitu,
11th Ketian Festival of Fools
13th Brabarian Feast of Brewing
14th Trifon Zara Zan (elven blessing of vines)
17th St Baalice's day
18th Festival of Thor the Ice Giant King (barbarian*)
23rd Buffalo dances (Rel Mord)
28th Up-helly-aa (barbarian* fire festival)
 
 

February

Middle of Spring

((Nyr Dyv floods))
1st Sapatu
1st Wives Feast (barbarian)
5th Birth of Apophis (Ketian)
5th St Rasha's Day (Feast of the Firefirghters)
6th St. Dorthea's Day
7th Queen's Celebration (Celene)
11th Feast of Asarat Abydos (Ketian)
13th Aerdian festival of purification begins)
14th St. Ansur's Day
14th  Vernal Equinox (Earth miracles double effect, No Air miracles)
15th-28th  Days of Danger (Istaritu travel and give warning)
15th Celebration of the Prelate of Almour
20th Barbarian gathering
21st Aerdian Festival of Purification ends (Anshar forgives all sins by the decree of the Overking)
23rd Terminalia (Nyrundian aniversary of Enmerkar's proclamation)
24th St Sunniva's Day
25th Day of Nut (Ketian)
25th Time of the Old Woman Begins (barbarian bad weather period)
26th Hygea's Day (Gulan male ceremony of purification)
 
 

March

Last Month of Spring

1st Sapatu
1st Matronalia (Marriage ceremonies of Ishtar)
2nd St Chad's Day
4th Time of the Old Woman ends (barbarian)
5th Celebration of Isis (Ketian)
6th Festival of Flowering Time (Barbarian)
7th Aerdian Festival of Fire
8th Birthday of Kishar
10th Holi (elven spring festival of lights)
10th Last Feast of the Spring (Beer)
12th St Gregory's Day
12th Celebration of Pholtus (Greyhawkian/pagan)
13th Purification Feast of Baccob (Greyhawkian/pagan)
14th Warrad-wurm (Aerdian Festival of Armour Making)
15th-21st Pentecost, Warriors of Sin Quest
16th Sixth Gahabar (mages)
17th Festival of Mephistopholes (Aerdian)
18th Sheela's Day (barbarian*)
19th Feast of Lahamu & Lahamia
20th Feast of Ba-nab-dedt (Ketian god of sexual fertility)
22nd Aerdian Festival of
23rd Summer Finding (barbarian)
25th Aerdian Laughing Day
25th Feast of Matri Stral Zhemla (mages)
27th Smell of the Breeze Day (Ketian)
28th Rahasia Alvere's Birthday, Traditional Fesitival of Ishtar
 
 

April

First Month of Summer (this month nether creatures roam free)

(( Red Star appears in Northern sky))
1st Sapatu, Festival of Ishtar, Lion fights (Babylon)
2nd Lion Fights (Babylon), Master of the Walls Celebration
2nd Beginning of New Year (Mages)
3rd Lion Fights, Celebration of the Daemon War (Babylon)
4th Lion Fights, Celebration of Ketian attacks (Babylon)
5th Lion Fights, Celebration of Desert battles (Babylon)
6th Lion Fights, Feast of the demon war (Babylon)
7th Feast of s'Naelix (Aerdian)
12th Supplication of the Overking begins (Aerdian)
13th Old Aerdian Festival of Liberties
14th Sommarblot (barbarian summer festival)
15th Festival of Bast (Ketian)
16th Feast of St. Cuthbert
17th Aerdian Marbles Festival
20th Avendasora (Celebration of the Tree of Life) (Babylon)
21st Building of Rouxes
21st Feast of Ufect (Ketian)
24th Children's Day (barbarian)
25th St Mark's Day
 
 
 

May	Middle of Summer

1st Sapatu
1st Birthday of Anshar
4th Battle of Stonefist Day (Barbarian)
6th Bigby's Day
9th Overking's birthday
11th St Mamertuis' Day
12th St Gregarin's Day
12th Elven Forest Festival
13th Lahamu & Lahamia Festival Day (Aerdian)
14th Summer Solstice (Fire miracles doubled, No Water miracles)
15th Ninurtan rain dances
15th Great Feast of the Southern Heavens (Ketian)
15th This-kin (Babylonian Festival of the thri keen invasion)
16th St Brendan the Navigator
17th Festival of Anshar (Aerdian)
21st Day of Tefnut (Ketian)
21st Zagig's brithday
22nd Ragnar Lodbrok's Day (Barbarian who tamed the Black Ice)
23rd Aerdian
28th Frigg's Day (barbarian)
 
 

June	Last Month of Summer  Height of plague season

1st Sapatu
1st Celebrationof trade pacts (Babylon & Chendyl)
4th Nanna Sin's Birthday
5th Sheela na Gig's Day (barbarian)
6th Night of Observation in Jalpa (Ramman, Aerdian)
9th St. Al'Akbar's Day
11th St Barnabas Day
11th Shammash's Birthday, Day of the Sun (Aerdian)
12th Festival of Mut (Ketian)
13th New Evermorean Festival of the Arts
14th Birthday of the Countess of Urnst
16th Feast of the Goddess of Lopolla (Ketian)
17th New Evermorean Day of Marriage
18th Judgement Day of the Annunaki
19th Waa-laa (elven)
20th Martyrdom of Iron Skegg (barbarian)
23rd Day of Cu-Cullain (barbarians)
24th Shammash's Birthday, Day of the Sun (Nyrundian)
24th Lucky Day (Greyhawkian/pagan)
27th Death of Gaentavish Moran (Aerdian champion)
27th Day of the Seven Sleepers (Ketian)
29th Secong Gahambar (mages)
 
 

July	First Month of Autumn

1st Sapatu, Nyrundian Fasting begins
1st Celebration of Holy Swords, Conquest (Babylon)
3rd Day of Sothis (Ketian)
4th Heir of Urnst (Countee and Duchy) birthday
8th Feast of St. Sunniva
9th Feastival of Unnar the Deep Minded (dwarven)
5th Feill Sheathain (elves)
11th Feast of Min (Kettian)
11th Feast of Lahamu & Lahamia
14th Birthday of Asar (Ketian)
16th Birthday of Set (Ketian)
17th Tisha be-Av (barbarian)
18th Birthday of Nepthys (Ketian god of death)
18th Birthday of Mordenkainen
19th Ketian New Year
20th Day of St. Cuspa
20th Binding of Wreathes (Lahamu & Lahamia)
21st Nyrundian Day of Prayers
21st Wizard colleges meet.
22nd Huricane Supplication Day (Ninurta)
22nd Charrissa Soothra's birthday
23rd Beginning of Dog Days (Ketian)
23rd Aniversary of Lord Soothra and Archbishop Alvere
27th Nyrundian Pilgramages, St Anda's Day
28th Start of Gathering Time, Domhnach Chrom Dubh (barbarian)
 
 

August

Middle of Autumn

1st Sapatu
6th Festival of Thoth (Ketian)
7th Breaking of the River (Ketian)
11th Puck Fair Begins (male barbarian fetility rite)
12th Lights of Isis Festival (Ketian)
12th Grape Festival (Beer)
13th Puck Fair Ends
13th-15th  "Starfall" (rain of shooting stars) begins, +5% miscast on spells
14th  Autunmnal Equinox (Air miracles doubled, No Earth miracles)
15th Birth of Isis
17th Amentarus Festival (Ketian)
19th Minerva's Day (Aerdian)
21st  St Dalvernar's Day
22nd Feast of Montu (Ketian)
24th St Jalpa's Day
26th Aerdian day for Tiamat
27th Procession of Bast (Ketian)
 
 

September

Last Month of Autumn

1st Sapatu
1st St. Keogtum's Day
2nd Feast of Asar Unnerfer (Ketian)
4th Anpu Transforming Ritual (Ketian)
7th Festival of Druaga (Aerdian)
10th Ketian Day of Queens
11th-17th "Starfall" ends
12th Third Gahambar (mages)
13th Ceremony of Fire Lighting (Ketian)
14th Ketian Feast of Lights
15th Sin's Birthday (Birthday of the moon)
16th St. Ninian's Day
17th Festival of Sabek (Ketian crocodile god)
19th Day of Gula
19th Fast of Thoth (Ketian)
21st St SuManda's Day
22nd Day of Ki (Aerdian)
27th Day of Willows
 
 

October

First Month of Winter

1st Sappatu
2nd Feast of the Gardian Spirits (Druidic)
5th Wine Festival (elven)
6th Feast of the Virgin Ahludam (Ninurtan snow queen)
7th Feast of Shu (Ketian)
12th Fourth Gahambar (mages)
13th Floating of the Lamps (elven)
14th Vinternatsblot (barbarian)
16th Cera Festival (Barbarian)
18th Festival of Herne (barbarian)
20th Festival of Ancestors (Sulaman)
25th St. Hammurabi's Day
27th Owalgt (Gulan women's healing ceremony)
28th Fyribod's Festival (barbarian festival for bag weather & winter)
30th Dedication of Lost Souls
31st Dark One's Day, Night of Wolves, All Hallow's Eve (Saints go to pay homage to the gods, no interventions)
 
 

November

Second Month of Winter

1st Sapatu
1st All Saints Day
1st Assembly of Tara (barbarian)
1st-5th Red Star Disappears from the southern sky
2nd New Evermorian Festival of Salvation, Day of Swords
3rd Barbarian New Year
4th Archcleric's Great Mass in the Theocracy
5th Wuwichim (Trigolese and Chendylese fire ceremonies)
6th Birthday of Tiamat
7th Ketian festival of ploughing
8th Gwynn ap Nudd Day (barbarian)
9th Feast of the Four Crowned Martyrs (Aerdian)
9th Loy Krathon (elven feast of lights)
13th Isis resurects Osirus (Ketian)
14th Winter Solstice (Water Miracles Doubled, No Fire Miracles)
14th Feast of the Musicians (Druidic)
17th Feast of St. Hilda (Nyrundian women's feast)
21 Day of Cailleach (barbarian old veild woman)
22 Ydalir (barbarian* winter festival)
23rd St Uptananishiptim's Day
24th Feast of Burning Lamps (Ketian)
26th Splednard's Birthday
 
 

December

Harshest (last) Month of Winter

1st Sapatu
1st Day of the Banshees (barbarian)
6th Mandrake Mandragoran's Birthday
8th Feast of the Immaculate Conception of Charissa Al'vere (Old Red)
12th Sada (mages)
14th Festival of Dramiji
16th Festival of Ea
22 Feill Feinnan (elvish)
23rd Secret of Unhewn Stone (barbarian feast of potential)
25th Festival of Astarte (Asmodeus after 520) (Aerdian)
28th St Cuspa's Day (Aerdian)
28th Birthday of Ra
 
 
 

In Greyhawk, the practice of Wizardry is tied to the stars and constelations.
A succesful astrology check at -2 to learn the correct time of day and proper alignment of the pentagram will
increase the hit die summonable by 2.
Astrology checks may also be used to determine astrological effects of the month.
Typical effects might be: (each last for one week of the year and correspond to the stars)

January
1. Wizards may employ wizardry to do a contact higher plane (towards their alignment)1/day
2. Wizard may summon an additional hit die of demon, may not summon Heavenly creatures
3. Chaotic wizards are at +1 to test of wills, Lawful wizards are at -1
4. summoned chaotic creatures do not return for an additional 1-3 days (wizard does not have control)

February
1. Summonings take twice as long, cannot summon daemons
2. demons summoned are at +1 per hit die, +1 all rolls
3. demons may freely cross a Protection From Evil or Protection From Demons *
4. summoned creatures from the lower planes do not return for an additional day (wizard does not have
control)

March
1. a quazit or imp also comes through when a lower planar creature is summoned (does not return)
2. good wizards are at +1 on the test of wills v.s. all creatures
3. good wizards are able to summon an additional 4hd of any type of creature, Homage begins in the Hells
4. creatures summoned by good wizards remain twice as long

April
1. good wizards may not be harmed by lesser demons, devils, or daemons
2. evil wizards are able to summon an additional 5hd of any type of lower planar creature
3. quazits and imps summoned by evil wizards will remain for the week, keeps in contact with overlord
4. daemons summoned are at -1 on their test of wills#

May
1. devils summoned are at -1 on their test of wills#
2. demons summoned are at +1 on their test of wills*#
3. devils summoned are at +1 on their test of wills#
4. 10% chance that something else comes through the gateway*

June
1. 15% chance that a Power is offended by the summoning*
2. summoned creatures from the middle planes do not return for an additional day (wizard does not have
control)
3. daemons are able to walk freely and uninhibited by Protection From Evil and Pentagram spells.
4. wizards who practice in this week are at -1 on all saves*

July
1. summoned lawful creatures do not return for an additional day (wizard does not have control)
2. creatures summoned from the upper planes are at +2 per hit die and +2 on all rolls
3. may petition plane of alignment for bonus to saves for chosen month in return for the wizard performing a
service
4. no detection or information spells work on creatures from the outer planes

August
1. duration of summoned evil creatures is doubled,
2. duration of summoned neutral creatures is doubled, +1 on saves v.s. fire
3. duration of summoned good creatures is doubled,
4. duration of summoned creatures is halved

September
1. Neutral wizards are at +2 to test of wills and +2 to hit die summonable
2. evil wizards who practice this week are at +1 on all saves and test of wills, cannot summon C.G. upper
creatures
3. neutral wizards who practice this week are at +1 on all saves and test of wills
4. good wizards who practice this week are at +1 on all saves and test of wills, cannot summon devils
creatures

October
1. wizardry requires double the time to summon a creature but they stay twice as long, - 1 to hit die
summunable
2. wizardry requires triple the time to summon a creature but they stay 3 times as long, -3 to hit die
summunable
3. wizardry is unable to summon this week
4. wizardry requires double the time to summon a creature but they stay twice as long, - 1 to hit die
summunable
4.b  (28th - 31st wizardry fails for entire period without a successful astrology check at -3 (one roll for the
period), +1 on hit die*, +10 HD on summonings from lower planes, otherwise as 40)

November
1. summoned creatures from the upper planes do not return for an additional day (wizard does not have
control)
2. upper planar creatures summoned are unaffected by Pentagrams and Protection From Good or Dispel
Evil
3. upper planar creatures are at +1 on all rolls and +1 on test of wills
4. wizardry is fails without a successful astrology attempt at -2 for each summoning

December
1. (1st-3rd) wizardry fails without a successful astrology check at -6 for each summoning, -1 on test if wills
and HD sum.
1b. (4th-7th) wizardry fails for entire week without a successful astrology check at -3 (one roll for the
week), +1 on hit die*
2. wizard may summon creatures from limbo who are 2HD larger*
3.a. (15th-17th) creatures from limbo remain twice as long under the control of the wizard*
3.b. (18th-20th ) creatures summoned from limbo do not return when task is done, stay on this plane for 1
day (no control)*
4a. wizard gaines 1 minor at will power for the week from 1 creature summoned (25% chance/summoning)
4b. (Dec 28th) wizard may try to petition plane of alignment for 1 new spell for the week (wise to give gifts)

October 31st (All Hollows Eve) - Saints Pay Homage to their chosen god, will not answer calls for divine
intervention. The forces of evil usually hatch many plots on the Prime Material Plane this day. "The Dark One's Day"

*=chance that wizard is brought to creatures plane is double i.e. treat wizard as half lvl for this purpose
#=succesful astrology check made at beginning of week outside and under a night sky gives +1 on HD
summonable

An eclipse of the sun will cause wizards to lose control of their subjects.
Each of the solstices are good for summoning particular types of elementals:
Summer Solstice: +6 to hit die summonable of Fire elementals, +2 hp/die, stay twice as long
Winter Solstice:+6 to hit die summonable to Water elementals, +2 hp/die, stay twice as long
Vernal Equnox: +6 to hit die summonable to Earth elementals, +2 hp/die, stay twice as long
Autumnal Equinox: +6 to hit die summonable to Air elementals, +2 hp/die, stay twice as long
Comets can have varying effects but usually signify the downfall of Kingdoms or Kings
It is said that seeing a shooting star during a summoning is a beneficial omen. Few wizards fail in this
instance.