ReadonlyChag, yontiff, yom tov
Candle-lighting for Chanukah
Chol haMoed, intermediate days of Pesach or Sukkot
Observed only in the Diaspora (chutz l'aretz)
Daily page of Talmud (Bavli)
Daily Learning
Evening before a major or minor holiday
Daily Hebrew date ("11th of Sivan, 5780")
Observed only in Israel
Light candles 18 minutes before sundown
Light candles in the evening at Tzeit time (3 small stars)
Yom Kippur and Tish'a B'Av
Minor fasts like Tzom Tammuz, Ta'anit Esther, ...
A holiday that's not major, modern, rosh chodesh, or a fast day
Mishna Yomi
Yom HaShoah, Yom HaAtzma'ut, ...
Molad
Nach Yomi
Days of the Omer
Weekly sedrot on Saturdays
Rosh Chodesh, beginning of a new Hebrew month
On the Saturday before Rosh Chodesh
Shabbat Shekalim, Zachor, ...
Yahrzeit or Hebrew Anniversary
Daily page of Jerusalem Talmud (Yerushalmi)
Yizkor
Yom Kippur Katan, minor day of atonement on the day preceeding each Rosh Chodesh
End of holiday (end of Yom Tov)
Holiday flags for Event. These flags are typically combined using bitwise arithmetic to form a mask.