Complex sentence: National Persian Gulf Day is a very important day for the Iranian people and it is celebrated on April 30 th every year since 2004, and is marked with various ceremonies all over Iran, especially in the coastal cities of the Persian Gulf.
Split into simpler sentences: National Persian Gulf Day is a very important day for the Iranian people and it is celebrated annually on April 30 th. It has taken place every year since 2004, and is marked with various ceremonies all over Iran, especially in the coastal cities of the Persian Gulf.