This year, the first day of spring -- also known as the vernal equinox -- falls on March 20. Here's what you need to know about the occasion.<div class="feedflare"> <a href="http://rss.cnn.com/~ff/rss/cnn_travel?a=C2ZR-VaeqQk:ccfkzAQ-88g:yIl2AUoC8zA"><img src="http://feeds.feedburner.com/~ff/rss/cnn_travel?d=yIl2AUoC8zA" border="0" /></a> <a href="http://rss.cnn.com/~ff/rss/cnn_travel?a=C2ZR-VaeqQk:ccfkzAQ-88g:7Q72WNTAKBA"><img src="http://feeds.feedburner.com/~ff/rss/cnn_travel?d=7Q72WNTAKBA" border="0" /></a> <a href="http://rss.cnn.com/~ff/rss/cnn_travel?a=C2ZR-VaeqQk:ccfkzAQ-88g:V_sGLiPBpWU"><img src="http://feeds.feedburner.com/~ff/rss/cnn_travel?i=C2ZR-VaeqQk:ccfkzAQ-88g:V_sGLiPBpWU" border="0" /></a> <a href="http://rss.cnn.com/~ff/rss/cnn_travel?a=C2ZR-VaeqQk:ccfkzAQ-88g:qj6IDK7rITs"><img src="http://feeds.feedburner.com/~ff/rss/cnn_travel?d=qj6IDK7rITs" border="0" /></a> <a href="http://rss.cnn.com/~ff/rss/cnn_travel?a=C2ZR-VaeqQk:ccfkzAQ-88g:gIN9vFwOqvQ"><img src="http://feeds.feedburner.com/~ff/rss/cnn_travel?i=C2ZR-VaeqQk:ccfkzAQ-88g:gIN9vFwOqvQ" border="0" /></a> </div><img src="http://feeds.feedburner.com/~r/rss/cnn_travel/~4/C2ZR-VaeqQk" height="1" width="1" alt="" />