I would like to call your attention to a missing Israeli national holiday in your Hebcal holiday list. Specifically I am referring to Yom HaAliyah. It is Israel's newest national holiday.
Yom HaAliyah should be listed in HebCal on the10th of the Hebrew month of Nisan. The 10th of Nisan is when the Torah says Joshua crossed the Jordan with all of Am Yisrael at Gilgal, and that is the official date of the new Israeli national holiday according to the bill passed by the Knesset on June 21st, 2016.
I don't know if you want to add it also, but the Yom HaAliyah bill mandates that schools in Israel also teach about Aliyah on the 7th of Cheshvan near Lech Lecha because on the official Yom HaAliyah date of the 10th of Nisan, the schools are not in session.
MK Micki Zohar in Knesset on the passing of Yom HaAliyah into law:
To copy/paste the Yom HaAliyah bill's first clause "of course its in Hebrew:
Thank you for adding this. It is crucial as many public calendars use and trust your website when setting their dates.
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