Retrocession Day is the day when the control of a specific land is transferred between two big countries, just like sharing a toy between two siblings. It happened in Washington DC, which is the capital city of the United States, and is also known as a special place because it was once a land that belonged to an area in Maryland. However, Maryland decided to give this land to the United States government to form a capital city.
Retrocession Day was the day when this land was returned back to Maryland because the United States government did not want to be responsible for some parts of the city like the jails and the hospitals. So, they returned it back to Maryland because they thought Maryland could do a better job at taking care of these things.
From then on, the land became part of Maryland again, but the United States government still uses it as their capital city. This is why Retrocession Day is a special day in history, as it marks the transfer of control and management of land between two important places.