I know this is a relatively old thread but thought I would chime-in on the issue of setting up annual (or yearly) rainfall using VWS and a Davis weather station.
First of all, as far as I know, the only way to change the daily, monthly and annual rainfall reports is to manually edit the data files. This is not a simple thing to do. However, before any of these changes will work correctly on an annual basis, you must change the RAIN SEASON BEGINS setting on the Davis console itself. VWS only collects the data it gets from the data files. To change the RAIN SEASON BEGINS setting, go into setup mode (Press DONE and the "-" console key) and then, using the DONE key, keep pressing it until you reach the RAIN SEASON BEGINS setting on the display. Then, using the + or - keys, select the month for the start of the rainy season. When finished, press and hold DONE until the current weather screen appears.
NOTE: This setup process does not change any rainfall data. It only sets the console up so it will reset everything at the beginning of each RAIN SEASON selected above. So, it may take as long as a year for your yearly rainfall data to get in sync unless you manually change the data files.