For you using the beta, we have now added a (very) basic time interval setting.
Just enter two dates to change the range in the graph. Right now we are limiting the data to a few thousand measure points, so you might not be able to view the whole selected interval in the graph. Since we are storing fewer data points further back in time (every third hour vs every 5 minutes), you might for example be able to see the graph for a whole year two years back, but only a few months back at a time if you start from today, since the number of data points is the same.
To access this function you need to use the new test version of the sensors-page, available at http://live.telldus.com/sensor/index2
If you find any problems, except from design issues, with the graph or the index2-page (it should load much faster), please let us know.
Remembering those sweet summer days...
If you are not using the beta yet, it's still possible to sign up here: http://developer.telldus.com/blog/2015/03/24/sensor_history_beta