What is a interested change date?

If you mean "what is an interest change date" it means the date when the interest rate on a loan changes when the loan is an "adjustable" or "floating rate" rate loan. A lot of home loans, for example, are "ARMs" or adjustable rate mortgages, and change usually on an annual date. Some debts are so related to interest rates that they may change every time the interest rate it is "tied to" changes, such as loan where whatever the prime rate of interest is "from time to time" is the interest rate, and "from time to time" literally could mean once every day if it changes that often!