"The Sub-Tropic of Sagittarius"
This flag can be flown anywhere along a special line of latitude known as the Milky Way Inner Core Sub-Tropic of Sagittarius: which is approximately 28.9 degrees south. Likewise anyplace on Earth that resides along the 28th parallel south can fly this flag anytime. For the rest of the planet, one can only fly this flag during the month of April and May, because that is when the core of the Milky Way Galaxy appears in the night sky.
Nations that can fly this flag all year round include: Australia, South Africa, Namibia, Brazil, Argentina, Chile, and French Polynesia.