'hereby begin' is correct and usable in written English.
You can use it to begin a document that demonstrates or declares something. Example: We, the undersigned, hereby begin this petition to call on the government to take immediate action against climate change.
The video shows Colbert behind the podium saying it's his honor "to hereby launch and begin the 2016 Republican hungry for power games" and banging a gavel.
"It is my honor to hereby launch and begin the 2016 Republican National Hungry for Power Games!" Colbert shouted at the podium, dressed like Hunger Games host Caesar Flickerman, according to an audience-shot YouTube video posted Sunday night.
My regrets to Dana Milbank, who writes, I hereby pledge that, beginning on Feb 1 , 2011 I will not mention Sarah Palin — in print, online or on television — for one month.
"I'm hereby directing the Department of Defense and Pentagon to immediately begin the process necessary to establish a space force as the sixth branch of the Armed Forces.
The economy will get better, unemployment will begin to take a downward turn, I predict, hereby, by the time warm weather comes, and the world will seem different and cheerier.
In the interest of historical accuracy, then, just in case the Diamondbacks beat the Yankees in the World Series, the moment their quest began is hereby presented in the words of the man who created it.
Any useful idiot even remotely tempted to begin arguing that, as a recovering addict, Brand is a worthy witness is hereby advised to stop being so bally silly.
Within the Army, officers had become terrified that James Thornwell's story would leak, and in August, 1962, just before the team departed for Hawaii, to begin the operation, the Army intelligence command at Fort Holabird issued a stern warning: "You are hereby instructed that under no circumstances will you use or allow to be used EA 1729 on U.S. citizens".
Well, let me begin by saying that this is the best residency I've done, and probably the strangest, but I hereby welcome offers for others!
At the end of the meeting, the official said, Mr. Bush gave the go-ahead to the commanders to begin the war at the time they judged best, saying, "For the peace of the world and benefit and freedom of the Iraqi people, I hereby give the order to execute Operation Iraqi Freedom.
