Why are there no beginning of spring in some years?

There is no "beginning of spring" in the whole year, and 19 will appear seven times. For example, 199 1 Year of the Sheep, 1994 Year of the Dog, 1997 Year of the Ox, 2000 the Year of the Loong, 2002 Year of the Horse, 2005 Year of the Rooster, 2008 Year of the Rat, 20 10 Year of the Tiger and 2008.

There will be seven periods in 19, such as 199 1 Year of the Sheep, 1994 Year of the Dog, 1997 Year of the Ox, 2000 the Year of the Loong, 2002 Year of the Horse, 2005 Year of the Rooster, 2008 Year of the Rat and 2005.