Formula For Daily, Weekly And Monthly Averages

Column B Column S

11-12-12 $500
11-12-12 $750
11-13-12 $100
11-17-12 $250
11-28-12 $100

So there are days with multiple values
Column B Dates
Column C values

for the daily average, you can use averageif()
for the weekly and monthly, add 2 extra helper columns,
in the 1st, use =WEEKNUM(B1,1), then use the averageif() function based on that
in the 2nd, use =month(B1), then use the averageif() function based on that

If you still have a problem, upload a sample workbook and I will walk you through it