Is it grammatically correct to include a date in an invitation as August 28th? Or should it be August 28, 2011, or 28th of August?

It is best to say, “August 28.” While we read that as, “August 28th,” it is written without the “th.”

And you can include the year if you want to. People who get the invitation are sure to know either way. But if it’s a keepsake or scrapbook item to somebody, they’ll like having the year.

August 28 or 28 August. Either or.

It’s not about grammar. It’s not even about English. It’s about date formats. There’s a European and an American version. The Brits and Germans do it the same way: day followed by month followed by year. Pretty straightforward. Easy to sort. And then there’s variants with the word “of”.

This format, 28 August 2011, is suggested in “The Elements of Style,” but I prefer the August 28, 2011 format. No “th” after 28, though.

Totally your option. Date should be included is my belief.