The expression "blue moon" is used to describe the second full moon that occurs in the same calendar month, or the fourth full moon occurring in a calendar quarter (trimestre), which usually has just three full moons (one per month).
This year, the moon was full on July 1 and on July 31. The next blue moons — two of them — will occur in 2018. By yesterday morning, you could clearly see that the moon had started waning.
By the way, we finished the cleaning of the garage. I took two carloads of stuff to the recycling center, and now the car is full again with stuff that I plan to take this week to the charity shop called Emmaüs over in Romorantin.
It's too bad I didn't take any "before" pictures. Cleaning out the garage is obviously something we do only once in a blue moon. Take my word for it — the garage is a lot emptier and cleaner now than it was last week.