Somewhere circa 600 B.C, the idea that the God of Israel has set a date for a judgment of all unbelievers enters into Judaism and becomes an integral part of it, Christianity and Islam come into being much the same as our TL, and still become 2 of the most powerful religions on the planet.
However, they still maintain the set date, Christians interpreting it as Jesus' return, and Muslims as the day of Allah's judgment, through all of these three faiths disagreements and wars, they maintain that the things foretold on this date will come to pass, as it is very clearly written in scripture.
The date? When interpreted to fit our modern calendar,it is October 18th, 2025.
History precedes the same as OTL, with evangelism and warning of the end times growing to a fever pitch as the fabled date approaches.
It comes...and nothing happens.
How does the world respond?
(Keep in mind that everything is the same as OTL, except for this element of doctrine.)