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Due to lack of canonical information in the franchise, there is no definite answer to this question.
There is no way to tell exactly how much. Starting on the morning Po wakes up from his dream (the film's opening sequence), a little more than two days pass before the training montage between Po and Shifu. At that point, the training might have taken a few days, or even a few weeks. After that (starting on the morning [or possibly late afternoon] setting during the sparring match with the dumpling), about one day passes before Po defeats Tai Lung and the movie ends.