I'm looking to start our first Adventure next week, but before I start I would like to know what year we are in. I'm going to print a calendar of that year to keep track of days as we go through the adventures and campaigns.

The calendar I'm using is from http://www.gmtools.excelocms.com/calendar.html.

This seems to come up weekly. A proper search of the forum will find numerous threads on this topic. Nevertheless, I'll tell you the answer, although you probably won't like it. It is not defined.

Many point to the map in the rulebook being label circa 2521 and assume it is therefore 2521. However, that doesn't account for the fact that there is a story about a Chaos Cult in the ToB (pg. 25 to be exact) that notes that the the cult met for the last time on Hexentag, 2522, thereby putting this date in the "past" of whatever the current day setting is. Therefore it must at least late 2522. Since the Storm of Chaos (as documented in 2nd ed) erupted in 2521, I take this as evidence to support my theory that the SoC has been retconned out of the setting and that the clock hasn't simply been rolled back to pre-SoC as many others have suggested.

Different parts of the book(s) point to different dates.

In some places they talk about a growing threat up North and name some of the characters involved in GW's Storm of Chaos campaign, as if to suggest it's on the horizon. In other places they talk about there having been a war and the north of the Empire recovering.

They also mention rat invasions of Talabheim, which is a veiled reference to a WFRP 2nd edition campaign / book which definitely took place after the Storm of Chaos.

On the "different parts different dates" indeed. In Eye for an Eye, Adnreas vanished "a year and a day" in past (page 72), which is 5 years after he was handed keys in 2515 (page 71) = 2521

Another clue to the year is in the Rulebook p 90 last part of the Karl Franz section. Here it states: "When uncountable Chaos Hordes devestated the north, the Emperor lead his troops to a victory not seen since the Great War against Chaos"

It is not much to go from, but it must refer to the Storm of Chaos 2521-2522, however I get the impression that these events have been downscaled in the WFRP3 edition, most likely to avoid having this cataclysmic event overshadowing all and everything going on.

It also looks like FFG has been avoiding dictating the precise year. For my own campaign, I run it in 2524-2525 which work well for me with the adventures published so far.