What was it?

When Jesus made this promise to the church in Philadelphia:

Revelation 3:10 Because thou hast kept the word of my patience, I also will keep thee from the hour of temptation, which shall come upon all the world, to try them that dwell upon the earth.

It has been mentioned a lot, that this is prophetically looking at the Christians escaping the tribulation by the blessed hope.

I believe that too.

However, Jesus is speaking to an actual church in John's day, making this promise.

So, there must have been some worldwide hour of temptation in their day, that Jesus kept this church from.

What was it?