The Tanabate of China, who can tell me the meaning of the western's tanabate?

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it is said that 'niulang' and 'zhinv' will be met today every year.'niulang'(man)and 'zhinv'(women) is a couple of lovers who can see each other only once a year. we call it ---Chinese Valention's Day. i want to know the meaning of western's tanabate. i think it must tell a moving story of love. dose anyone tell me ? thanks.