annual evaluations in the block "Rain"

[ToMe]

Hi gius
I started recording weather data in August 2012. Therefore I miss the months January to July of the year. Now my questions: Do the missing values affect the annual evaluations, for example in the block "Rain"? And if so - is there a possibility to set the start of the evaluations to a certain date, in my case to the beginning of 2013?
Thanks for your help.

Torsten