Why is Yom Kippur is on the 8th of the 7th month? What is so special about this day that it was separated from all other Shabbats?
I am not quite sure but I do have some thoughts about it that I wanted to share.
Just in case you missed it, I explained why it is on the 8th and not on the 10th here. But why the 8th?
First of all, it is interesting to note that 8th of the 7th month is exactly 6 month from the 8th of the 1st month when we are supposed to take Passover Lamb. Obviously there is a connection between these dates. I think connection is in terms of atonement for sins. We atone for sins on the 8th of the 7th which can be said to resemble our redemption from Mizraim.
The phase of the Moon on Yom Kippur is 1st Quarter (dark side on the left, light side on the right) is to remind us monthly about this event of the 7th month. So Yom Kippur is on the 8th because it is the only available Shabbat in the 7th month (all other are taken by other Holy Meetings) and because 8th is the Shabbat and Yom Kippur is explicitly stated to be the Shabbat.
Also, the 7th month is called "revolution" or "turning point" of the year. See Exodus 23:16 and Exodus 34:22. This means that the 7th month is the middle of the year, since we know that the 1st month is the beginning of the year (Exodus 12:2).
So why do we have Day of Atonement in the middle of the year?
I think it maybe because God wanted to lessen our sin burden to the minimal amounts by having us to atone in the middle of the year, so that we have to carry just half-a-year worth of sins, as the sins begin to accumulate from the beginning of the year. So even though it does not change anything, such simple mathematical trick helps to reduce the sin burden by 50%. This would be a scientific answer to the question.
And of'course, there is a connection to the circumcision, since it also happens on the 8th day. I think all these events are connected in terms of sin and atonement for it. I.e a circumcision is an atonement for the original sin.
What do you think?