The Blood of Vol has a different Calendar (the Qabalrin Wheel), it contains a thirteenth month that corresponds with Crya (the moon of dal'quor).
Since the length of the year should not change (otherwise you have summer in Vult every 12 years) how does the additional month change the other Months?
(i don't have access to my campaign setting/guide right now)
Greetings,
Laures
I'm actually pretty sure it does not change it in anyway. It just adds a month to a year and nobody cares. Of course I'm probably wrong, but I'm still pretty sure it does not change anything.
I don't think it says in the books.
I just assumed a change from a solar to a lunar calendar.
It does say that they only use the Qabalrin Wheel to set faith related dates (holidays, rituals etc). And they still use the Galifar Calendar for any real world dealings: so they may not care if they "drift" into a summer in Vult every 12 years (in any case - with the Children Of Winter around, you may get winter in any month of the year anyways 
).
It's been said that that each moon gets brighter in it's corresponding month.
I'd end up treating it like a holiday-month, similar to RL Ramadan, to avoid headaches. That doesn't really jibe with the lore regarging the literal thirteenth month. Maybe Cyra's disappearance altered the other moon's orbits, slowing them down or lengthening them? Then the years would be the same length, the months would have been five weeks of five days, with 11 days "left over"? That'd mean Cyra would "wander" now...
Check pg 80 of Faiths of Eberron, top left paragraph, first column:
"The wheel has thirteen months rather than the standard twelve, with the last - Cyra (sounds familiar?), associated with the lost Mark of Death - coming after Vult and before Zarantyr on the Galifar calender. This renders the Qabalrin Wheel year one month longer than the Galifar year"
So long story short, yeah things are going to be different with the Qabalrin Wheel calender.Using the wheel is going to leave people with (to them and their strange 12-month'ed'ness) a wonky view of the year.
But as has also been posted, the Blood of Vol uses the Galifar calender to indicate key liturgical events of the year. They do however have a different starting point (as opposed to YK). They use the fall of House Vol as the reckoning point for their calender. So while it's 998 YK for the greater majority, the Blood believes it to be 2398 FH (2398 years since the Fall of the House).
In the real world many religions use a different calander system to our everyday one to determine the dates of religious events, typically using a lunar calander instead of our solar one. This causes religious festivities like Easter or Ramadan to 'drift' with respect to our 'normal' calander. The Qabalrin Wheel could have the same effect.
On the other hand Faiths of Eberron mentions that the thirteenth month of the Wheel always occurs at the same time relative to the Galifar calander, so perhaps the Wheel's months just have a different length compared to the Galifaran months. (Note that although Faiths seems to be implying that the Wheel uses the Galifaran months for the other twelve months, it actually does not say this if you read carefully. All it says is that the thirteenth month of the Wheel is called Cyra).
Maybe the year is longer for people using the Qabalrin calendar. It's a weird metaphysical thing, but in their personal version of the universe, shaped by their faith and a healthy consumption of blood, they actually have 28 more days.
Maybe the year is longer for people using the Qabalrin calendar. It's a weird metaphysical thing, but in their personal version of the universe, shaped by their faith and a healthy consumption of blood, they actually have 28 more days.
28 Days Later ...
"It was the blood, or something in the blood!" AHHHHHHHH xD