Date: September 11th, 2026 8:10 AM
Author: ...,,..;...,,..,..,...,,,;..,
Since the 9/11 attacks, the overlaps are:
2018 (5779): September 11 was Rosh Hashanah Day 2. Rosh Hashanah ran from sunset September 9 through nightfall September 11.
2026 (5787): this year: Rosh Hashanah begins on September 11, at sunset Friday evening. So September 11 is Erev Rosh Hashanah during the day and the first night of Rosh Hashanah after sunset. Day 1 is Shabbat, September 12.
2029 (5790): September 11 will again be Rosh Hashanah Day 2, ending that night.
2037 (5798): September 11 will again be Rosh Hashanah Day 2.
So, as of today, September 11, 2026, this is only the second 9/11 anniversary that has actually overlapped Rosh Hashanah: 2018 and 2026. The distinction is interesting: 2018 was entirely Yom Tov on 9/11; 2026 becomes Yom Tov only at sunset on 9/11.
And before the attacks, 1999 also had September 11 as Rosh Hashanah Day 1 (and Shabbat).
(http://www.autoadmit.com/thread.php?thread_id=5902601&forum_id=2Elisa#50128886)