I'm trying to have my spreadsheet to sum up values by month. Note that the dates are not organised chronologically. I've tried the solutions showing here but they are not working for me. I'm not really good at this.
Please try putting the start and end dates (say in G1 and H1) and a formula such as:
Alternatively, since all your dates appear to be this year, you might extract the month number with something like:
copied down to suit and then create a pivot table with that number for Rows.
1) add a helper column which calcluates the month eg =date(year(A2),month(A2),1)
2) Use the Format > More formats > More date and time formats feature to show the helper column as month and year
3) Use the Data > Pivot table report feature to make a summary table
Here's a worked example: https://docs.google.com/spreadsheets/d/1VIeA4zAjID0y1jo1FnsbfGA4qmpRgAxMykLXi1pOfhc/edit?usp=sharing