Shemini Atzeret is the 8th day after the 7-day Feast of Tabernacles. It concludes the Year of Biiblical Feasts of the LORD and three (3) days after it the Reading of the Torah also resets back to Bereshit, the beginning in Genesis.

In the Menorah -idiom, the Feast of Tabernacles sits in the candle on the opposite side of Unleavened Bread and Shemini Atzeret - The Day after Tabernacles, fits into the pattern of Passover being The Day before Unleavened Bread.

Celebration of the Dedication of the Altar

2 Chronicles 7:8-10
’Also at the same time Solomon kept the feast seven days, and all Israel with him, a very great congregation, from the entering in of Hamath unto the river of Egypt. And in the eighth day they made a solemn assembly: for they kept the dedication of the altar seven days, and the feast seven days. And on the three and twentieth day of the seventh month he sent the people away into their tents, glad and merry in heart for the goodness that the LORD had shewed unto David, and to Solomon, and to Israel his people. ’

The Feast for seven (7) days is the Feast of Tabernacles, so the Shemini Atzeret, the 8th day, falls on 23rd of Tishrei.
Counting back from the beginning of Feast of Tabernacles, the Altar in the 1st Temple was dedicated for seven (7) days, hence that dedication ended on 14th and begun on 7th of Tishrei.
When Yeshua, Jesus, was on the Cross in Nissan 14th, that ended the dedication of the Altar of the 3rd Temple

Six (6) days before the Cross on Passover, Mary of Bethany annointed Jesus for sacrifice. Here the link to my video with Gospel comparison and visual notes on that specific event:
https://www.youtube.com/watch?v=7kF46VUOgwU

Celebration of the Dedication of the 3rd Altar on Shemini Atzeret 2026?

Could it be that the celebration idiom of Solomon sending people to their tents on Shemini Atzeret is an allusion to the Rapture? The parallel with the first Feast of Passover (one (1) day Feast) with the last feast of Shemini Atzeret (one (1) day Feast) weaves all the Biblical Feasts together starting with the Dedication of the Altar, sacrifice on that Altar and then the Celebration of that Dedication on Shemini Atzeret. Just like the candlestands on the Menorah are connected first to last, second to second to last and so on with the stem being the Holy Spirit poured out on the people after Jesus ascension, connecting the Trinity to ONE in the Stem of the Menorah.