On this day 70 years ago, Oct. 9, 1940, John Lennon was born in Liverpool. It’s undeniably tragic that he is not around to celebrate his birthday today. But this can also be a happy occasion for fans, a time to reflect on all the joy that this great artist brought into the world before his senseless murder in 1980.

The 70th anniversary of Lennon’s birth is being marked around the globe in all kinds of ways. EMI rolled out a major reissue campaign of his solo catalog earlier this week — read all about it here. Last fall’s complete Beatles remasters still sound amazing as well. If you’re not up for buying any of those CDs, iTunes is offering a free download of “(Just Like) Starting Over” from the new Double Fantasy Stripped Down. This fresh version of one of his best-loved tunes, without some of the studio dressing from the original 1980 release, is well worth adding to your iPod.

There’s plenty of Lennon love elsewhere on the Web, too. Google‘s homepage has been decorated since yesterday with a cute animation based on Lennon’s drawings. Over at YouTube, you can check out video tributes to Lennon from his widow Yoko Ono, his old bandmate Ringo Starr, and fans from Brian Wilson to Jeff Bridges to the Jonas Brothers. You can also submit your own clip paying homage to Lennon if you like.

If you live in New York City, consider heading to Central Park’s SummerStage Theater tonight for a special free screening of a new documentary about Lennon’s years in the city, LENNONYC. Doors open at 6 p.m. for the 7 p.m. screening. (If you’re not based in NYC or you can’t make it, don’t worry — PBS will air the film Nov. 22.)

Those are just a few of the many options available for honoring Lennon today. Will you be celebrating his 70th birthday? Let us know how in the comments.

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