So how do days, weeks, months, work in Westeros

[Lord Spark of House Spark]

It sounds like there is one piece of the puzzle you are missing: the original cover blurb to AGoT and some of the PR material for the series when it started explicitly said that the seasons on the planet had once been 'normal', presumably meaning like ours. A 'preternatural event' disrupted the seasons and they have remained disrupted ever since. Fan speculation has been that either the Long Night and the beginning of the war with the Others 8,000 years ago, or even the Children overreaching with magic when they destroyed the Arm of Dorne 12,000 years ago (both by the accepted chronology, itself highly suspect), is what threw the seasons out of balance.

Because the seasons were once normal, that gave the Children and the First Men something to base 'a year' around. Cultural inertia has kept it as 12 moons = 1 year ever since. This is not entirely convincing (that the fact there used to be 'normal' seasons has been lost even to myth, whilst the same calendar system from those days has survived intact) but I see it as GRRM trying to keep things simple and fudging it a bit.

GRRM has also said we will get an explanation for why the seasons are out of balance in later books. Some have speculated that the final defeat of the Others (if that happens) may restore normal seasons to the world.

As for why the seasons oscillate so much, one theory is that the summers are long and warm when R'hllor's power is in ascendance and he is winning his struggle against the Great Other, and the winters are long when the reverse is true.

this sounds like the best explanation we are going to get. I was trying to come up with a highly volcanic moon with a 365 day orbit, glowing kind of like a second sun, but I couldn't quite get it to work to explain the length of a year, and it would have been odd for no-one to have mentioned it. although I think jhirri spoke about a second moon of legend that was where the dragons came from?

I am sure I saw a reference to a fortnight somewhere, with typical Westerosi dodgy spelling, but I can't find it.

I think it was something to do with something that happened a fortnight afterJoffrey's name day tornament maybe?

the point is would this be 14 days?

the obvious way that days should have been named in the common

tongue is after the seven gods, which would suggest 4 week months and a reason for a name for a 14 day period.

[Rhaenys_Targaryen]

this sounds like the best explanation we are going to get. I was trying to come up with a highly volcanic moon with a 365 day orbit, glowing kind of like a second sun, but I couldn't quite get it to work to explain the length of a year, and it would have been odd for no-one to have mentioned it. although I think jhirri spoke about a second moon of legend that was where the dragons came from?

I am sure I saw a reference to a fortnight somewhere, with typical Westerosi dodgy spelling, but I can't find it.

I think it was something to do with something that happened a fortnight afterJoffrey's name day tornament maybe?

the point is would this be 14 days?

the obvious way that days should have been named in the common

tongue is after the seven gods, which would suggest 4 week months and a reason for a name for a 14 day period.

“Mormont said as we should track them, and we did,” Gared said.

“They’re dead. They shan’t trouble us no more. There’s hard riding before us. I don’t like this weather. If it snows, we could be a fortnight getting back, and snow’s the best we can hope for. Ever seen an ice storm, my lord?”

Robert shook his head. “I have never seen a man sicken so quickly. We gave a tourney on my son’s name day. If you had seen Jon then, you would have sworn he would live forever. A fortnight later he was dead. The sickness was like a fire in his gut. It burned right through him.” He paused beside a pillar, before the tomb of a long-dead Stark. “I loved that old man.”

It had taken her a fortnight to marshal her courage, but finally, in bed one night, Catelyn had asked her husband the truth of it, asked him to his face.

“When I must. Preparations must be made. It will be a fortnight before we are ready to depart. I would sooner let Jon enjoy these last few days. Summer will end soon enough, and childhood as well. When the time comes, I will tell him myself.”

There you go :) Several fortnights from the first few chapters of a Game of Thrones alone. There are more though. It is mentioned often enough!

I like you idea that the days were fashioned after the gods (one day for each god), giving a week seven days, making a Westerosi fortnight the same af ours, namely two weeks! :)

[JungWheats]

The root of the seasonal dysfunction will have to be addressed in the end of the story, elsewise nobody in Westeros is going to live through the Winter. Even if they beat back the Others or succeed in any type of military endgame, the continent doesn't have any food. Dorne will probably be fine, but if the snows from the North become typical for most of the continent, then everyone will pretty much die. The Narrow Sea will have terrible storms and possibly frozen ports and a starving population working the docks, so anything imported has to cross the Narrow Sea, survive storms, evade the Iron Born, pull into port, and then have a population with the strength to unload everything. Armies have eaten or destroyed everything in the fields in the Riverlands, the North's chance to harvest is over. If the 7Kingdoms continue to breakdown, the Stormlands and the Reach will begin infighting instantly due to all of the long-held grudges and historically stolen and restolen kingships, etc etc. Westeros has no food. If Winter is going to last 10 years, nobody will survive.

So, whatever it was that created the seasonal imbalance, has to be resolved. For me, my money is on some magic used by the Children against the First Men, or a failed (or sabotaged) attempt at humans replicating Children's magic, or whatever created dragons, as they are obviously a magical race of creature and therefore, not natural in a way.

[Stannis Eats No Peaches]

We know that months last the same amount of time because periods are called "moon blood" because they happen once every lunar cycle.

[Lord Spark of House Spark]

Mormont said as we should track them, and we did, Gared said.

Theyre dead. They shant trouble us no more. Theres hard riding before us. I dont like this weather. If it snows, we could be a fortnight getting back, and snows the best we can hope for. Ever seen an ice storm, my lord?

Robert shook his head. I have never seen a man sicken so quickly. We gave a tourney on my sons name day. If you had seen Jon then, you would have sworn he would live forever. A fortnight later he was dead. The sickness was like a fire in his gut. It burned right through him. He paused beside a pillar, before the tomb of a long-dead Stark. I loved that old man.

It had taken her a fortnight to marshal her courage, but finally, in bed one night, Catelyn had asked her husband the truth of it, asked him to his face.

When I must. Preparations must be made. It will be a fortnight before we are ready to depart. I would sooner let Jon enjoy these last few days. Summer will end soon enough, and childhood as well. When the time comes, I will tell him myself.

There you go :) Several fortnights from the first few chapters of a Game of Thrones alone. There are more though. It is mentioned often enough!

I like you idea that the days were fashioned after the gods (one day for each god), giving a week seven days, making a Westerosi fortnight the same af ours, namely two weeks! :)

Thanks. It was the Jon Arryn one I was thinking of. It stuck in my mind at the time because I couldn't remember any mention of a Week, or a Sabbath.

[TalalOfDorne]

It seems to operate on a lunar-year system, though from what I know, a lunar year is usually something like 11 days shorter than the solar year.