A flag day is a flag-related holiday, a day designated for flying a certain flag (such as a national flag) or a day set aside to celebrate a historical event such as a nation's adoption of its flag.
Flag days are usually codified in national statutes passed by legislative bodies or parliaments; however, in some countries a decree or proclamation by the head of state or chief executive can also order a flag day.
The statute, or the proclamation or decree, may specify locations where flags are to be flown and how (for example, at full- or half-staff); alternatively, custom may prevail.
Nations that are not broadly recognized sovereign states are shown in pink.
Defunct states are highlighted in light grey.