If you read Matthew 24 you will see that the tribulation was local to Jerusalem and Judaea.; that Christians were to run to the mountains when they saw Jerusalem surrounded by armies, and to pray that their flight would not be in winter or on a Sabbath day. This event was to precede the destruction of the temple and city (not one stone left on another) followed by the dispersion of surviving Jews to all nations. This happened in 70 AD as an unrepeatable event.
Matthew 24 and Luke 21 are parallel passages which should set your mind at ease that Jehovah's Witnesses have no idea how to interpret biblical prophecy and never have.