A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
You could use SUMIFS, COUNTIFS and AVERAGEIFS.
Let's say your date is in A1, you have dates in column C and amounts related in column D.
=sumifs(D:D, C:C, $a$1)
will give you the sum of values in column D when column C matches A1.
You could use SUMIF instead of SUMIFS, but the former is a lot more powerful, and you would only have to learn the sintaxis for one of them.