Averageif data is in first part of a month

Hi guys, I have a data set spanning 2 years. I would like to average all of the values that occur in the first 1/3 (Day1-10) a second average on the second 3rd (Day 11-20) and a final average for the third 3rd (Day 21-28or30or31). Can anyone help me write the equation for such an idea?

The average ignores the month and year and just averages values in the range of days.

I am having trouble loading a sample spreadsheet.
But lets say that the date was in cells A3:A9 and values to be averaged were in cells B3:B9.
Enter this formula in column C
=day(A2)
Copy that formula all the way to the end of the data. (Cell C9 in my example)

Then enter three average formulas under data in column B. (Cells B11, B12, B13 in my example)
First Third Avg =AVERAGEIF(C3:C9,"<11",B3:B9)
Second Third Average =AVERAGEIFS(B3:B9,C3:C9,">10",C3:C9,"<21")
Third Third Average =AVERAGEIF(C3:C9,">20",B3:B9)

Note the "Second Third Average" uses the averageifs function.

Thanks NikkiSB. I was missing the quotation marks.

Cheers.