The other date linked to this story is - September 11, 1638.
The earliest story dates to 1683, during the Ottoman Turks siege of Vienna. Legend has it that a baker working late at night heard the Turks tunneling under the walls of the city and alerted the military.Many people have heard that the croissant was created in 1686 in Budapest, Hungary by a courageous and watchful baker, at a time when the city was being attacked by the Turks. Working late one night, he heard odd rumbling noises and alerted the city's military leaders. They found that the Turks were trying to get into the city by tunnelling under the city's walls. The tunnel was destroyed and the baker was a hero, but a humble hero — all he wanted in reward was the sole right to bake a special pastry commemorating the fight. The pastry was shaped like a crescent, the symbol of Islam, and presumably meant that the Hungarians had eaten the Turks for lunch.
The military collapsed the tunnel in on the Turks and eliminated the threat, saving the city. The baker baked a crescent shaped pastry in the shape of the Turk’s Islamic emblem, the crescent moon, so that when his fellow Austrians bit into the croissant, they would be symbolically devouring the Turks. Source.