The pope made the remarks as he celebrated mass at St Stephen's Cathedral in central Vienna, on the last of his three-day visit to Austria.
He said the day should be set aside for reflection on faith and the many threats humanity poses to the world.
The Pope also made a veiled comment about man's destruction of the environment, calling for people to celebrate God's creation at a time when creation seems endangered through human activity.
Pope Benedict is due to complete his visit with an address to Catholic volunteer groups today.
