Day of Valdemar and Reunion Day is observed in Denmark every June 15. This holiday commemorates two significant historical events that occurred on the same date in different centuries. The Day of Valdemar, established in 1912, celebrates King Valdemar II's victory in the Battle of Lyndanisse against Estonia in 1219, during which the Danish national flag, the Dannebrog, is said to have fallen from the sky. Additionally, on June 15, 1920, Denmark reunited with Southern Jutland, a region that had been a point of contention between Danes and Germans since the 19th century. The struggle for this territory included conflicts in 1848 and 1864, culminating in a referendum that divided Schleswig into Northern and Southern Schleswig, with Northern Schleswig being transferred to Denmark. The holiday is also known as Flag Day, reflecting its connection to national pride and historical remembrance.