Sentence:  <WSD>Spring</WSD> Festival" throughout East Asia because it is reckoned as the beginning of their <WSD>spring</WSD>. 
Meaning of the word marked with <WSD> tags:  The period from the moment of vernal equinox (around March 21 in the Northern Hemisphere) to the moment of the summer solstice (around June 21); the equivalent periods reckoned in other cultures and calendars.