The modern Syriac people have been celebrating the Akitu or Assyrian-Babylonian new year for decades, both in their homeland and around the world. There are tens or even hundreds of articles and documents telling the story of Akitu.
Ancient Assyrians-Babylonians celebrated the Akitu Festival over 12 consecutive days. Here is what traditionally happened on each day.
Day One: On this day, Assyrians dedicated their time to praying to the gods, after which they start preparing for the second day's festivities.

Assyrian traditional dress Source: aap.jpg
Day Three: Before sunset, priests would be praying, then the people would join the prayers. Then the king would bring the statue of Nabu son of Marduk and take it inside the temple to be worshipped.
Day Four: The high priests start telling stories about the creation. The general public would be singing and dancing. This day is a day of memorial and celebration.

todays assyrians carring the tradition Source: Ajannc.jpg
On his arrival, the king would be escorted to the temple by the high priest. There, the king got off his throne, removed his imperial gown and knelt in front of the gods to tell them that he had no sin or ill-feeling against them, his people and his kingdom. This ritual symbolised humbleness.
Then the priests accept the king's confession and put his royal attire back on, and reintroduce him to the public and the celebration starts again.

The procession of the King and Queen Source: AANF.jpg
Day Seven: On this day, god Marduk would disappear, and nobody would know his whereabouts. This means he went to fight with goddess Tiamat. Now he is imprisoned in the mountains of the universe, then god Nabu with other gods will go on a mission to rescue him.

Assyrian festivals costume Source: AANF.jpg
Day Nine: The king will be in front of a huge procession with gods featuring on floats, covered with gold and precious blue stones. In the first float, there will be four priests to assist god Marduk. The second float would be the royal carriage drawn by three horses, followed by other floats.

How the festival is celebrated today. Source: AANF.jpg
Day 11: On this day, the gods would perform a ritual of Determination of Destiny for humanity for the coming year.
Day 12: On this final day of the festival, the gods would return to the temple while people continue to celebrate.