Let's consider the facts concerning this misconception. Begin with the Book of Daniel, chapter 12, verse 10...
10. Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.

    What?! The Bible says that none of the wicked shall understand during that time. Does it only say that in the Book of Daniel? No, let's look in Revelation, chapter 9, verse 20...

20 ... And the rest of the men which were not killed by the plagues yet repented not of the works of their hands, that they should not worship devils, and idols of gold, and silver,and brass, and stone, and of wood: which neither can see, nor hear, nor walk.

    Note that the phrase "the rest of the men" is all-inclusive, it means all of them, and it says that they "repented not", in total agreement with the statement made in Daniel 12:10.

    Revelation, 16:10 & 11...
10. And the fifth angel poured out his vial upon the seat of the beast; and his kingdom was full of darkness; and they gnawed their tongues for pain,
11. And blasphemed the God of heaven because of their pains and their sores, and repented not of their deeds.

    These three scriptures completely refute the misconception that anyone who was not saved gets saved during the tribulation of those days. You must note that this is not opinion, it is Bible scripture, directly quoted and rightly divided.