The day when we remember and celebrate the coming of the Holy Spirit (Acts 2).
Have we forgotten the Holy Spirit?
Francis Chan (his book Forgotten God) argues that we have forgotten him.
Not that we deny him. But he is not a real part of our lives.
"While no evangelical would deny His existence, I'm willing to bet there are millions of churchgoers across America who cannot confidently say they have experienced His presence or action in their lives over the past year. And many of them do not believe they can." (page 15).