It was signed on June 4, 1920.

The Treaty of Trianon and the Communist Romania

"The Treaty of Trianon was the peace agreement signed in 1920, at the end of World War I, between the Allies of World War I and Hungary" -

You may be referring to the Treaty of Trianon.

Trianon

There were four separate treaties. Treaty of Versailles was signed by Germany, Treaty of St. Germain was signed by Austria, Treaty of Neuilly was signed by Bulgaria, and Treaty of Trianon was signed by Bulgaria.