Mostly a south Indian festival, Vishu is the dawn of a new astronomical year, and the day marks the first day of the Malayalam month of Medam that corresponds with April in the Gregorian calendar.
They will issue a refund and depending on the method of refund, this should be completed within 28 days. You will be asked to return all documentation regarding the gap insurance you have cancelled and the cover will cease at this point.
For those who file an amended return, however, the period to receive a refund check will take 8-12 weeks. For efilers (e.g., those who file electronically) here is a refund cycle chart that gives target dates when either an electronic direct deposit or mailed paper check should be expected given a particular filing date.