An example file with a description of which date, and types of groups would be helpful.
In the mean time, here are several articles about grouping dates in pivot tables. Maybe one of them will solve your problem
Group By- **50 Things You Can Do With Excel Pivot Tables** ****https://www.myexcelonline.com/blog/50-things-you-can-do-with-excel-pivot-tables/
Pivot Tables in Excel are one of the most powerful features within Microsoft Excel. A Pivot Table allows you to analyze more than 1 million rows of data with just a few mouse clicks, show the results in an easy to read table, “pivot”/change
the report layout with the ease of dragging fields around, highlight key information to management and include Charts & Slicers for your monthly presentations.
**** Topic 20: Group by Date
Topic 21: Group by Quarters & Years
Topic 24: Filter by Dates
Group by Age Range / Group A Pivot Table By Age Range****Run time: 2:47 ****In this video we look at how to group sample voting data into 10 year buckets, using a pivot table.
Group by Date / Group Dates in a Pivot Tablehttp://excelchamps.com/blog/group-dates-in-a-pivot-table/****Creating a group of dates in a pivot table is one those awesome features. With this, you can instantly create insightful and ready to present reports. When you work with a data where you have dates in it, the best thing to summarize it in months, years,
or quarters. ET MR PivotTables.docx
Group by Date / Group Dates with a Pivot Table
https://www.myexcelonline.com/blog/group-dates-with-a-pivot-table/
Grouping Dates is very easy with a Pivot Table. All you have to do is Right Click on your Date values (which are either in the Row or Column Labels of your Pivot Table), then choose the
Group option. From the dialogue box you can choose to Group by Days, Months, Quarters or Years.
ET PT PivotTables Power Query BI.docx
Group by Date / Grouping Dates in a Pivot Table VERSUS Grouping Dates in the Source Data**** 2016 05 11
Jon Acampora****https://www.excelcampus.com/pivot-tables/grouping-dates-pivot-table-versus-grouping-dates-source-data/
****Learn the differences between the Group Dates feature in a pivot table and grouping dates in the source data by adding extra columns for year, month, quarter, etc.
Skill level: Intermediate
Group by dates / Group an Excel PivotTable by dates 2014 10 27
Susan Harkins
https://www.techrepublic.com/article/pro-tip-group-an-excel-pivottable-by-dates/
Grouping lots of data by dates is easy using Excel's PivotTable. Susan Harkins shows you how.
A PivotTable is a great way to summarize a lot of data. The technical side of things is simple — you insert a PivotTable and add the appropriate fields. If you're grouping by dates, you'll have lots of options, but all of the possibilities aren't as obvious
as you might like. In this article, I'll show you how to group a PivotTable by date components. I'll also show you a few of the less-than-obvious possibilities.
* Group by date components
* About those weeks
* 2013 new filtering feature called timelines