Maybe the economic calendar is vague or comes with no benefits for some people as we can see above comments however in my opinion it allows us to note which currency has major event that leads to liquidity injections. We can conclude many beneficial things from this single calendar.
It's the best, most comprehensive, allows for filtering according to the importance of the news event in terms of its impact on the market, easy to use and gets updated in real time when the news comes out. It's the best you can get without paying $10K for a dedicated feed from Bloomberg.
WHY ?!?!? WHY ?!?!? WHY ?!?!? WHY ?!?!? 90% of the time, currencies moved but the economic calendar didn't give any indication. 90% of the time, the economic calendar hilited major news/events but currencies hardly moved. The facts are so obvious even the blind can see. anyway, go and do your own analysis on usefulness / uselessness of the economic calendar. the creators of the economic calendar need to do a much better job.
Ok that's not the fault of the calendar. Currencies move or do not move according to their own reasons, sometimes related to the economic event(s), sometimes not. Don't kill the messenger just because you didn't like the result.
Oh, its a very important tool for someone who trades on the basis of the fundamentals. It definitely gives an insight about which currency pair will experience volatility during which major market event.