The immortal of the Tang Dynasty, but the game starts at Xuanwu Gate?

Three Hundred Tang Poems: Two Hundred Memories of the Glorious Tang Dynasty!
No one doesn't love this magnificent dynasty, just as no one doesn't miss the glorious Chang'an of that time!
This was an era interwoven with poetry and song, an era of blood and fire!
The camel bells of the Silk Road, the dim lights of the marketplace, the everyday life on the streets, and the fluttering banners on Zhuque Street—all paint a picture of ultimate splendor!
"..."
Chen Huai'an transmigrated and became a person forgotten by time.
He didn't know whether it was a blessing or a curse.
But he thought, this prosperous Chang'an should be taken a good look.
However, a very serious problem now lies before him...
Chen Huai'an (voice cracks): "What do you mean it's the ninth year of Wude, the third day of the sixth month, and the Xuanwu Gate team-building event starts tomorrow?"
"I'm still fucking under Li Jiancheng's command?!"