Final answer:
The YEARFRAC function in Excel calculates the fractional years between two dates, accounting for the number of days in each month and any leap years.
Step-by-step explanation:
The YEARFRAC function in Excel is a mathematical function that calculates the fractional years between two dates. It returns the number of years between a start date and an end date, taking into account the number of days in each month and any leap years. This function is commonly used in financial and business calculations, such as calculating interest or determining the length of an investment.