Mark Biltz posted a video recently called "When will the TRIBULATION begin? Where are we on the BIBLICAL Calendar?".
https://www.youtube.com/watch?v=4mTP36wQnvM

Mark  believes that the Tribulation can only start at the beginning of a Shemitah cycle.
We are currently in year 5781, the 6th year of the current Shemitah cycle.
Rosh Hashanah 2021 begins the 7th year of the current Shemitah cycle.
Rosh Hashanah 2022 begins the 1st year of the next Shemitah cycle.
If Mark is right, the Tribulation may start on Rosh Hashanah, 2022.  If not then, the next chance would be Rosh Hashanah, 2029.  Then Rosh Hashanah, 2036.
If true, this means the Rapture won't happen this year unless there is a year between the Rapture and the beginning of the Tribulation.

Some bad things have happened on the last day (Elul 29) of the 7th year of a Shemitah cycle (the Shemitah year).
On Elul 29, 2001, the Dow fell 7%.
On Elul 29, 2008, the Dow fell 777 points (also 7%).
I don't recall anything significant on Elul 29, 2015.
Who knows what may happen on Elul 29, 2022, given 15 more months of Biden.
If the Tribulation started on Rosh Hashanah, 2022 (with the Rapture), it could be preceded on Elul 29 by sudden destruction.

RH 2021 - RH 2022 would be the 7th year of the current Shemitah. Year 5782
RH 2022 - RH 2023 would be the 1st year of the tribulation Shemitah.  Year 5783
RH 2028 - RH 2029 would be the 7th year of the tribulation Shemitah.  Year 5789
1948/49 + 80 = 2028/2029 (year 5789).
If the Jewish calendar is off by 210 years because the years Israel was in Egypt were excluded, 5789 + 210 = 5999 (the end of man's 6000 years).

The first year of the current Shemitah cycle (RH 2015 - RH 2016) was preceded by the 2014/2015 blood moon tetrad:

4-15-2014 Passover
10-8-2014 Tabernacles
4-4-2015 Passover
9-28-2015 Tabernacles (super)

The first year of the next Shemitah cycle (RH 2022 - RH 2023) will also be preceded by a blood moon tetrad (although one is partial and none are on feast days):

5-26-2021 (super)
11-19-2021 (partial)
5-16-2022
11-8-2022

Perhaps these bookends mark 7 good years followed by 7 bad years?

The American eclipses could also fit into this scenario.

The August 21, 2017 total solar eclipse on Elul 1 served as a warning.
The April 8, 2024 total solar eclipse on Nissan 1 could complete God's judgement of America, signaling her destruction during the Tribulation.

The United States has certainly done nothing but get worse morally at an unbelievably fast pace since 2017.