Matthew 24:21 For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
Mark 13:19 For in those days shall be affliction, such as was not from the beginning of the creation which God created unto this time, neither shall be.

If we compare the Matthew 24:21 verse in question with the corresponding verse in Mark 13:19.
While both verses do say there has not and will not ever be a time like this.
The words tribulation and affliction are the same Greek word “thlipsis” mentioned in the article but as we can see only Matthew uses the word “great”.

So those that say there’s no 7 year tribulation, there’s only a 3 ½ year great tribulation on the grounds of this Matthew verse haven’t taken into account that the same verse in Mark doesn’t go along with that argument.
If this phrase “great tribulation” is so important, I’d expect to see it in both the Matthew 24 and Mark 13 scriptures but maybe that’s just me.
I would also expect it to say “great tribulation” in Matthew 24:29 if this phrase is so critical to our understanding of “End Times” but doesn’t.

There is no corresponding verse in Luke 21 as that discourse deals with the events in 70AD that were mentioned.

I believe it’s possible that the word “For” which is gar in Greek could be render as “Because”.
So if we take Mark and add the preceding verse in;
Mark 13:18 And pray ye that your flight be not in the winter.
19 Because in those days shall be affliction, such as was not from the beginning of the creation which God created unto this time, neither shall be.

The point I’m trying to make is this doesn’t necessary mean it’s the starting point of this “great tribulation” at the Mid-Point of Daniel 70th Week, it could already have started.

I believe the chronology of the Book of Revelation points out that the 6th Trumpet which is the 2nd Woe starts just before the Mid-Point and ends just after the Mid-Point.
So “The Day of The Lord” would have already started before the Mid-Point in this case.
I just don’t agree with the fitting of all the passages about the start of “The Day of The Lord” around this “Great Tribulation” verse.