A hybrid adjustable-rate mortgage, (also known as a "fixed-period ARM"), blends characteristics of a fixed-rate mortgage with an adjustable-rate mortgage. This type of mortgage will have an initial fixed interest rate period followed by an adjustable rate period. After the fixed interest rate expires, the interest rate starts to adjust based on an index plus a margin. The date at which the mortgage changes from the fixed rate to the adjustable rate is referred to as the reset date.