The sad think is that there aren't any special days or months that actually influence the behavior and the life of people , like holidays and that stuff.
( I know there was such a thing in Morrowind )
I was a super nerd when I started to play Oblivion and noticed that some times during certain months that the shops would open later then normal so I googled the months and holidays and this is what I found.
Morning star- January, 1st and 15th are holidays
Sun's dawn-February, 16th is a holiday
Rain's hand- April,28th is a holiday
Second seed- May,7th is a holiday
Mid year- June,16th is a holiday
Sun's height- July,10th and 20th are holidays
Last seed- August,27th is a holiday
Heartfire- September,3rd is a holiday (4th is my personal B-day in game and RL

)
Frost fall- October- 13th and 30th are holidays
Sun's dusk- November,20th is a holiday
Evening star- December, 15th and 30th are holidays
Weather or not this carried over from Oblivion-Skyrim I don't know and I haven't really noticed either.
