Google finance historical data prices error

[Jose Garcia]

Hi,

I find that historical prices of google finance contain some errors or
missing information.

Specifically, the Day "February 18, 2011 "the stock of apple has a
volume of 0 however the historical prices displayed on yahoo finance
the same day "February 18, 2011" shows a volume of 29,077,700.

I see that on Monday 21 February the market was closed. That may cause
the error of Google Finance?

Why does this happen?

I need reliable historical values for my software.

Thanks.