Your logic looks off.
HtmlNodeCollection weeks = doc.DocumentNode.SelectNodes("//table");
foreach(HtmlNode week in weeks)
HtmlNodeCollection tempdate = week.SelectNodes("//td[@class='t']");
for (int i = 0; i < 6; i++)
dates[i] = tempdate[i].InnerText;
In your code, every inner loop you loop through is just resetting the dates values when it loops through another HTMLNode (outer loop).
What do you intend to do with dates