The video sequence opens gradually--frame after frame capturing a tiny baby from the first day he entered the world at Harrogate General Hospital in Yorkshire, England. Then it races forward and literally becomes a life flashing before our eyes through pictures that dad Ian McCleod took of his son Cory essentially every day of his 21 years. He compiled the more than 7,500 images into a six-minute time-lapse sequence he posted on YouTube in late September. Corey's life from birth to becoming a young man has now been witnessed by more than 800,000 people around the world, and received 300,000 hits on one day alone in Japan.

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McLeod tells the Yorkshire Post the project started as a "daft" idea conceived over a couple of drinks. "I was thinking I could do it for one or two years at most…But then you get to the point you wonder if you'll regret it if you stop." He says it became like brushing his teeth.

Cory McLeod admits he didn't always love it when his dad tracked him down for their daily snap. "My dad's had to drive to a friend's house before. I got a bit of a stick [teased] for that," he told the Post. Eventually he came to see the project's significance. "I used to find it awkward, I didn't realize the value of it. It was only when I got to 16 or 17 that I started to appreciate it and realized what it could be." Even though he's now away from home studying at Leeds Metropolitan University, he says he plans on continuing to collaborate with his dad. "When do you stop? I don't think I can. We've come this far, we may as well carry on."

Although a few days are missing here and there (Ian McLeod slots in a sketch instead of inserting a photo from the wrong day to maintain the integrity of the concept) and a month was lost when the camera wouldn't wind, the chronicle is remarkably complete. McLeod started scanning the images a year ago-his son was born before the days of digital cameras-and he says it took him three months total to digitize them all. "It's never been straightforward," he says. "We weren't organized. It's always been chaotic." For those of us whose photo albums contain gaps of more than a year, '21 Years' seems magnificently pulled together.

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