C# Function to count minutes employees work per day based on date/time values

Hello, We have a time clock system where employees clock-in and the date/time is stored. We need to do a calculation on those punches to determine how many minutes per day that employee worked. The program we already have would pass a list of punches (say two weeks worth) and we need it to return a list of "Day" objects that tell us how many minutes that employee worked in a day. Please see the attached spec document for more info