I have a spreadsheet with the following 2 columns and 5 rows, just an example.

Month Date
April. 1
April. 2
April. 3
May. 4
May. 5

What formula can I use to format it as follows? Objective is to remove the duplicates.

Month. Dates
April. 1, 2, 3
May. 4, 5

This is just an example. The actual spreadsheet I need to work on has hundreds of rows with duplicates in the first column and different values in the second column. The objective is to remove the duplicates and show all of the values together separated by commas.

I can think of a way but it's not a formula.

* Data:Sort (by Date then Month)
* Data:Remove duplicates
* For each month, select the dates and do Paste Special:Transpose
* Delete the extra rows of months.