While the year is fraught with holidays and observances, some of the most in quantity and importance are in the springtime.
The natural world is literally abuzz with activity as the sun peeks out just a bit longer every day. We were treated to a lunar eclipse not long ago and can look forward to a solar one too shortly! In celebration of surviving another winter, we humans across time and continents celebrate the rebirth of our world as it dramatically comes to life before our very eyes. Personal twitterpations can run abundant, but our broad cultures and religions offer many other ways to enjoy the happenings of spring in a communal way.
Around the world we see a vast array of U.S.-originated Arbor Days to help usher in new life and a greener world. Japan is getting ready to celebrate its Golden Week which hold many interesting cultural and historical notes all while having a beautiful hanami picnic. The observances of Passover and Easter are also deeply important for many. Even (by definition and not insult) heathens have celebrated by way of Imbolc and Beltane, observing the timing of the vernal equinox and measure of the year's passing with nature itself.
Older civilizations than that have embodied this time in their pantheons too through such figures as Sumerian/Babylonian Ishtar and the Greek Persephone. Bringing us back to modern times and a more secular culture, we also can't forget May Day or its piggyback relative, International Workers' Day (which was also ingrained not just in a broad labor movement but Communist society).
Phew! There sure is a lot going on isn't there? All things natural, celestial, cultural, political, historical, and "us" seem to bloom this time of year. We also can't forget giving thanks to the one who helped usher us into and through the world: Mom.
Many other cultures and religions exist that weren't mentioned and I'd urge you to explore them. Learning about the Wheel of the Year, White Day, Sham el-Nessim, Abhidhamma Day, or Holi can only help you to appreciate the wonderful diversity of thought, religion, and culture that exists in our world. You'll notice I didn't hyperlink those as I'd urge you to use this as a jumping point in your own springtime adventure to enlightenment!
P.S. - No wikipedia was used either, which means each of the links provided can be plumbed for even more information if you get your mouse a-clickin' on each of them! How's that for an easter egg?