They say it's his birthday, to paraphrase an old pop song.

It's not easy to fathom, but John Lennon, who was born in Liverpool, England, on Oct. 9, 1940, would be 70 years old today.

To celebrate the milestone, a new monument was unveiled in Liverpool today to honor the singer-songwriter.

"We come here with our hearts to honor Dad and to pray for peace and say 'thank you' to each and every one of you," said Julian Lennon, 47. He attended with his 71-year-old mum (Lennon's first wife), Cynthia Lennon, who first met John Lennon at Liverpool Art College.

"Don't be morbid, enjoy the joy that he had, and what we all have from his music," she told the hometown crowd.

Fans across the globe are remembering the Beatles co-founder, who was fatally shot outside his New York City apartment building by a deranged stranger in 1980, shortly after turning 40.

Yoko Ono has asked YouTube viewers to post their own tributes, which you can watch here. PBS has produced the new documentary 'LENNONNYC' about the musician's final years, and all Lennon's solo albums have been remastered and re-released for the occasion. Today, a time capsule in Lennon's honor was dedicated at Cleveland's Rock 'n Roll Hall of Fame, to capture the Brit's wide-ranging influence on pop culture.