Code for downloading forecasts

Tried to download daily files from forecast.io, but I do not really
understand how the forecast into the past works. It does one of two
things

1) Looks at t-i from t0 and makes a call
2)actually goes to t-1 and makes a call.

Resolving this will remove all sorts of doubt.

Additionally, only 1000 api calls are free each day, perhaps consider
buying more? who knows if this would help.