Dates require their own set of specialized functions. They work differently than regular numbers requiring the user to take more care when using them in formulas.
Dates can be sorted to put a list in chronological order. They can be subtracted to find age or duration. Dates can also be used as multipliers in other calcuations such as determining interest on a bond.
Using dates and times in Google Sheets works differently than using numbers as well. Spreadsheets need their hand held a bit tighter in order to figure out what is a date or time and what is just a string of other characters.