2. Starting from the Winter Solstice, every nine days is divided into a segment, sequentially called the first nine, second nine, $\cdots$, ninth nine. The Winter Solstice of 2004 was on December 21, and the Start of Spring in 2005 was on February 4. What is the day of which nine is the Start of Spring?
2. The first day of the sixth nine-day period
2. 【Solution】 December has 31 days, January has 31 days, from the Winter Solstice to the Start of Spring, there are $(31-20)+31$ $+4=46$ (days)
$46 \div 9=5 \cdots 1$, the Start of Spring is the first day of the sixth nine-day period.