Today, 465 years ago, in the year 1555. Pope Paul IV, born in Naples as Gian Pietro Carafa, signed the evil antisemitic decree for Jews to wear yellow cloth to be recognized as Jews.

In Sefer Seder Hadoros, we find that on the 14th of Tamuz he ordered the following: “Every [Jewish] male, female and child must wear a yellow hat on their head, women must wear a distinctive yellow veil, even if commuting out of town. All Jews must live in a single-walled neighborhood, and at night the doors must be closed.” The list goes on and on, restricting services received by non-Jews, limiting Jews in their conduct of business, only allowing a single Shul in town, and so on. The decree was signed on the 14th of Tamuz, but was made public only a few weeks later, on… [you guessed it] Tisha B’av.

Source: Seder Hadoros 5315