The Calendar

A day in Ravnica is 24 hours. A week in Ravnica is 5 days. A month is 5 weeks long. The year is 10 months long (total 250 days.) The phases of Ravnica’s two moons, Sanguine and Pecunia synch up with the Calendar. Sanguine takes a week to complete a cycle and Pecunia takes a year. Moons are often visible from late afternoon until dawn.
Because of the 5 day/5 week structure it is a custom in Ravnica to indicate the day using a finger on on the left hand and the week using a finger on the right hand. (Start counting with the thumb.) So it’s only natural that in common usage people starting referring to the days of the week based on their fingers.
Days of the week: Prime, Point, Middle, Ring, Pinky
Weeks are referred to by number. The phase of Sanguine changes each day, completing a full cycle over the course of the week. The mid point of the week is marked by a New Moon. Sanguine is rarely observed during it's full moon at night (instead either at dawn of Prime or the dusk of Pinky depending on the time of year) and occurs so briefly that there is no day dedicated to it. The day of Sanuine's New Moon is observed as a day of prayer and tithe for the Orzhov, with the rare Middle Week eclipse being a penultimate holy day, taking on the manifestation of the Black Sunburst.

1. Waning Gibbous
2. Waning Crescent
3. New Moon
4. Waxing Crescent
5. Waxing Gibbous

The weeks are generally referred to as a suffix to a day. For example the 3rd day of the second week would be referred to as Mid-two. Or to communicate this using a hand gesture: With palms facing outward extend the middle finger of your left hand and the index finger on your right hand.
There are 10 months in a year. They are named as follows.

Month of the Demon: Pecunia is not visible (Waning New). This is the hottest month of the Year. This phase of the moon is sacred to the Rakdos because the blood moon is more prominent. On Month of the Demon, Prime-one the Hell Fire Bacchanalia is celebrated. The up scale precincts celebrate this holiday like New Years with drinking and merry making. The cult of Rakdos tradition is more like the Purge and often drags on into a week long Riot Carnival.

Month of the Boar: A tiny sliver of Pecunia is visible in the west. (Waxing New). It is slightly hot. This phase of the moon is sacred to the Gruul because of the prominent blood moon paired with the promise of rebirth as Pecunia peeks into view. For the old ways teach us that after Ilargh destroys Ravnica, a new and more natural world will flower from the ashes. On Month of the Boar Prime-one, the Gruul perform the Rites of Strength, known as Rauck-Chauv in the old tongue. Clans from all over the Rubble Belt will send representatives to district 10 to compete in contests of strength and skill. There is the airing of grievances and the lifting of heavy things. There is also a lot of drinking and fighting. This is a traditional day for teenage Gruul to perform the rites of passage into adulthood. Any non Gruul that celebrate on this day do so for the fighting and the drinking.

Month of the Rose: Pecunia is in waxing crescent. The weather is perfect all month long. This month is sacred to the Selesnya because of all of the new life that springs forth this lovely time of year. On the Month of the Rose, Prime-one: The Selesnya celebrate the Bounty of Nature. The Festival of Plenty is a Conclave tradition that celebrates community and prosperity. If you are not one of the prominent food artisans selected to spend all day preparing the feast you would spend the day performing random acts of kindness for your neighbors. The Selesnya Conclave traditionally unveils a large scale philanthropic project on this day. Typically they will work on that project all year long. The evening culminates in a huge feast where simple wholesome ingredients are transformed into a nourishing and delicious experience that transcends words.

Month of the Sphinx: Pecunia is in Waxing Half. The weather is getting crisp. This month is sacred to the Azorius because it was in this month that the Guild pact was created by Azor the Parun of the Azorius senate. The moon waxing represents the prosperity brought about by the law. The Half moon represents the balanced scales of Justice. On the Month of the Sphinx Prime-one: all true Guild Patriots will observe the Solemnization of the Guild Pact. This involves a lot of monotone voices reading from the same dusty tome every year. We must preserve our history to ensure our future. It is customary to fast on this day. When this custom didn’t catch on the Azorius made it a mandatory holiday for restaurants to observe. This is not the only reason that some people spend this holiday protesting the Azorius Senate. You have to do it peacefully if you want to make them look like the bad guys.

Month of the Mask: Pecunia is in Waxing Gibbos. It is called the Month of the Mask for the little sliver of darkness Pecunia wears on her face, like a mask. The weather drops rapidly throughout this month. It has become customary to honor the guild-less citizens during the Month of the Mask. Before the Dimir were known to be an active guild, this holiday appeared to dedicated to no guild, a preconception that suited the Dimir well. The guild-less share stories of their contributions to society. On The Month of the Mask Prime-one: The Great Masquerade is recognized. Any citizen is allowed to dress in any livery and everyone goes about wearing masks. It is customary for guilds to give anyone in the appropriate costume access to low level guild amenities. After all you never knew who you might be insulting if you turned them down. It is considered very rude to turn down a reasonable request by a guild member on this day and non violent chicanery is encouraged against prudes who don’t participate. Many guild-less citizens take full advantage of favors they are normally denied.

Month of the Coin: Pecunia is Waxing Full. Pecunia is the moon associated with money, so obviously the Orzhov claimed this month for their own. Immediately afterward they parcelled out the rest of the year and sold each month to its current owner. This is the coldest month of the year. On Prime-one the Observance of Obligations begins. A procession of Priests and Thrulls will leave Orzhova and walk through the streets gaining followers in their wake. After a critical mass of goons has been amassed they will walk throughout the entire city collecting on every outstanding delinquent debt. Those unable to pay will be compelled to join the procession. The debtors are degraded and paraded through the streets to the terminus at Medori Park in Precinct 6. The lucky delinquent debtors will leave with higher interest rates imposed and more valuable collateral placed on the line. Those who are not so fortunate will have to spend their body and soul to cover a debt that they do not want their relatives to inherit. On an average year this procession will take less than a week. Although the Orzhov will not end the procession until every last debtor has been accounted for. On a particularly poor year the Observation of Obligations lasted all month. When it threatened to interrupt the Triumph of Aurelia Parades the Boros grudgingly agreed to hastily aid the Orzhov in their debt collection efforts.

The Month of the Shield: Pecunia is in Waning Full (Still fully visible but she moves to the Eastern side of the sky.) This month is sacred to the Boros because the full moon resembles a round shield. When Pecunia moves to the east it appears that the blood moon is charging her every week and she deflects him 5 times. The weather starts out really cold but by the end of the month it’s just regular cold. On Prime-one the Triumph of Razia is celebrated with Military Parades. Aurelia is the Boros Parun. She has many triumphs. On this day we are celebrating all of them. It is customary to prepare food and drink to give the parading soldiers.

The Month of the Fish: Pecunia is in Waning Gibbos. The weather is wet and crisp. As the cold waters melt the Simic come out of hibernation and begin a new cycle of productivity. The tides are very favorable this month. Clean snow melt washes away some of the pollution from the previous year. Prime-one is the Day of the Flush. This day is observed by cleaning up the mess you made in the past year. The Simic will broadcast a list of people who caused the most pollution over the past year. It is polite to publicly shame these offenders if you see them during the rest of the month. Most citizens of Ravnica don’t know that every Pink-day in the Month of the Fish the Simic host a real hootenanny under the sea.

The Month of the Dragon: Pecunia is in Waning Half. When the red light of Sanguine hits the craters of Pecunia just right you can see the Dragon in the moon. The weather is wet and temperate. Prime-one is Niv-Mizzet’s (the Izzet Parun’s) birthday. This day is formally known as the Anniversary of the Dragon. It is customary to celebrate this day by taking risks. Many star crossed lovers will finally get the courage to give a gift to the one they have been secretly admiring. Extreme sports are arranged by the Izzet league. It is polite to purchase low grade explosives to light up the night sky until the following dawn.

The Month of the Beetle: Pecunia is in Waning Crescent. This position symbolises the last vestiges of life leaving the old husk before it is reborn into something new. The weather is wet and hot. Prime-one is the Celebration of Soil. Macabre parades wind through the streets in a sombre celebration of death. In your last hours rejoice for you will return to the soil and from the soil will spring new life. Revellers will paint their faces like zombies and imbibe mild poisons that have psychoactive properties. This is a day to find closure on the death of a loved one. Given their lives within the Undercity, few members of the Golgari observe the Lunar cycles but mark this day nonetheless, as their services are well sought after. From the provision of strange consumables to the much stranger commission of raising of the departed so that their loved ones may bid them farewell on their own terms (the aforementioned dressing as revenants and ghouls that happens this month does help to make the experience less traumatising).