It kinda depends on how ready you are for something a little bit more complex but it looks to me that your best bet would be either to create a DayStats class which would have properties for each of the values and could through serialisation be saved on a per day basis or, possibly a little easier depending on your experience, create a database which would enable you to preserve all entries in one place. By using the array, you are forcing many values into an unsuitable type (date especially), and making manipulation rather unweildy in the process.