In professional circles, the most common convention conveys dates in a month-first format. In this format, the month is spelled out, and the year, preceded by a comma, is a four-digit number. Writers may or may not employ a comma after the year.
This means the example sentence in the cropped graphic above is correct. Placing the comma after the year makes the year a type of parenthetical comment, and delineating parenthetical comments with commas is grammatically appropriate.
However, the final comma need not appear in the sentence. In that case, a writer could revise the example sentence in the cropped graphic above in this manner:
A convention commonly used in the military and growing in use in business and industrial circles avoids the use of the comma altogether by placing the month second in the order of elements in the format. Thus, September 12, 2015 appears as 12 September 2015.
Unless your audience demands the more traditional convention, using this month-second format provides the most clarity in communication while avoiding the confusion surrounding commas simply because commas do not comprise part of the format. Note the change in the example sentence from the cropped graphic above when the writer applies this month-second format.
Of course, writers should avoid using numerical formats for dates, especially in technical writing. These formats have always conveyed more confusion than clarity. Much of the world lists the month first when using a numerical format for dates, but Americans list the month second. Thus, the date from our example sentence could be 12/09/15 or 09/12/15. Just looking at the numerical format, your audience could wonder whether you mean September 12 or December 9. Writers expressing the most clarity with dates avoid numerical formats.
Writers conveying the most clarity with dates also avoid the use of commas. So clear your dates of commas for greater clarity. Greater clarity better communicates your message. And that more effective presentation will in turn more effectively promote you and your brands in the minds of your audience.