In Brazil, it's traditional for its citizens to wear white when celebrating New Year's Eve. Given the fact that Jewel's broken wing, in the first movie, may have at least 3 months for being healthy and able to fly, the time Blu and Jewel had until the breeding season (which is in November), and the hatching of the eggs, that should bring us to January. Plus, the chicks fledge lasts about 2 months, now it is March. Therefore, their children weren't able to celebrate with their parents the New Year, and they should have waited for the next year. With these facts, it's presumable that roughly 2 years have passed since the events of Rio.