"The Obscurial was here? Where did she go?"
-- Percival Graves
Five Aurors attempt to capture Gellert Grindelwald at his remote, derelict chateau somewhere in Switzerland. The five approach the chateau only to be blasted by a “sudden explosion of pure white light” that throws them back and appears to have killed them. From this confrontation, Grindelwald travels to the United States of America to track down an Obscurial which he saw in a vision. Once there he impersonates Percival Graves, one of the most powerful Aurors in MACUSA, and tries to find out who the Obscurial is.
The date of November 28, 1926, was on the newspaper seen in the film just after the attack. The headline read "GELLERT GRINDELWALD Dark Wizard Strikes Again in Europe." Since the attack happened at night, we are assuming that this newspaper story appeared the next day. Of course, since this newspaper is a prop created by MinaLima and not written specifically by Rowling, the date is at best an approximation. Rowling's script doesn't list a date. It does, however, state the that next scene with the ship gliding into New York harbor happens the next morning, and newspapers seen in the main lobby at MACUSA headquarters that day say are dated December 6th.