And further to this in order to make it even more confusing:
If I use an explicit range - ie 2012-01-01 - 2012-01-31 it works fine - it's when I say "This month", "last month", "next month" etc then this is when I get this "start from the 2nd" behaviour....
Would you be able to post the workbook or a sample workbook where you are seeing this (saved as a twbx file)? Thanks!
This could still be date epoch issues - I've had problems in the past from a single source where I've created a calc, created an extract, created another calc and suddenly the date between the two are different as the date calculations are switched to Tableau vs. Jet.