You have multiple options.
You can use ToShortDateString()
method for the DateTime
type
lb[i].Text = dt.DayOfWeek + " : " + dt.Date.ToShortDateString()
or you can provide of a format to the ToString("format")
method to specify exactly what you want it to look like.
lb[i].Text = dt.DayOfWeek + " : " + dt.Date.ToString("MM/dd/yyyy");