Can someone read production week from this serial? The serial looks like this

a13038xxxxxxxxxx

I know that I have to look for 3rd digit for the year, and 4th and 5th for week of that year to get the week when my iphone was made. 

Do I count the first letter or not? Or I start form the first digit after the letter 'a'?
The iPhone 3GS model number is A1303, so I'm guessing that if you're looking at your serial number, it's somewhere with the model number appended to the beginning. To see just your serial number, go to Settings > General > About.

Once you have your serial number, the 3rd character will be production year, the 4th and 5th characters will make up the production week.

For additional info, check out "iPhone Serial Number Secret (Decode Color, Size, Production Year and Week)" on My Digital Life.