Filters on Tablix in SSRS

Hello,

I am using the filter on the Tablix in SSRS:

Date_Results
Text
Between

.... for first report

=DateAdd(DateInterval.Day,-7,Today())
=Today()

I am getting 10/11/2012 until 10/17/2012 which is correct

but second report
=DateAdd(DateInterval.Day,-30,Today())
=Today()

As we are 10/18/2012, I was expecting the results between 9/19/2012 and 10/18/2012, but I am getting ONLY 10/04/2012 until 10/18/2012 ... ( I have data since 11/17/2010 almost 2 years)

any idea why?

Thanks,

Dom

System Center Operations Manager 2007 / System Center Configuration Manager 2007 R2 / Forefront Client Security / Forefront Identity Manager