Yud Tes Kislev is NEVER mentioned in: Tanach, Mishnah, Jerusalem Talmud, Babylonian Talmud, Rashi, Tosafos, Gaonim, Rishonim, Shulchan Aruch, or the commentaries written on pages of the Shulchan Aruch.
Yud Tes Kislev is NOT a real Jewish holiday, and should NOT be celebrated by Jews.
Don’t Jews already have enough holidays, even without Yud Tes Kislev?
Last-but-not-least, if you make new Jewish holidays, Ain LeDavar Sof — there is no end to it!