The phrase "during the first three weeks" is correct and usable in written English.
You could use it in a sentence like this: "I was sick with the flu during the first three weeks of January."
The survey was administered to 1,001 Catholic households during the first three weeks of October.
The Conference Board surveyed 5,000 households during the first three weeks of September to compile its report.
Great American Volleyball will conduct additional tournaments in Point Pleasant Beach during the first three weeks of August.
He adds: "It was a daily contact … I edited I think during the first three weeks of that campaign, it was a daily affair".
Internet shoppers spent $10.67, on average, for shipping during the first three weeks of the holiday season, BizRate says, or 37percentt more than last year.
In order to make sense of the party's advance, I have combined the results of YouGov surveys conducted during the first three weeks of October.
The report will probably be issued during the first three weeks of December because the offices of Major League Baseball normally shut down for the Christmas holiday week.
The league and the union mutually agreed to suspend testing in late October because the agreement's confidentiality provisions were breached during the first three weeks of testing.
Knowing that its defense was poor, it pushed everything forward, giving this World Cup more thrills during the first three weeks than any other team.
Younger siblings receive fewer feedings and less fish from parents, and during the first three weeks of life their weight is 11 percent lower.
The report points out that 12 people died of the H1N1 virus during the first three weeks of March, including six from Maharashtra (Daily News & Analysis).
