months

i understand that our modern yearly calendar is based off of the roman
months and days. so, how many 'months' are in the old norse calendar,
and what names are attributed to them? what would the month-names'
translations into american english be? was there a set number of days
for each month, or were the numbers of days irrelevant?

also, how would the old norse calendar compare to our modern calendar?

I ask this because i found a book that gives names for January,
February, etc - all 12 months. I don't think the author considered the
romanizing of the year when offering his monthly names and information.
My reasoning for this, is that the roman calendar didn't consistently
have 12 months in a yearly cycle until... Augustus, or Octavius??
(number of months adopted per Emperor is historic fact; "which one" is
irrelevant). Fact is, some roman years only had 9 "months", others had
10 "months".... So, what did the Norse have?

Please help. thanks.