If you’ve been ultra efficient and create a calculated Date Field that will display the month and year (e.g. Aug 2015) of a date column so that you can group something like News Articles in this way, you may have already discovered that grouping your list view using this new column displays the group header as blank. When you include the calculated field in your view, you see it has value BUT the won’t display in the group header.
I found a work around for this – simply edit your view and change the style to Basic Table. I also played around with default expansion of the groupings. This should now display your calc field group headings and display any items underneath.