http://columbia.edu has been crawled 2,569 times going all the way back to December 21, 1996.
A crawl can be a duplicate of the last one. It happens about 25% of the time across 420,000,000 websites. FAQ
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Note
This calendar view maps the number of times http://columbia.edu was crawled by the Wayback Machine, not how many times the site was actually updated. More info in the FAQ.