“Anno Phoenicis,” meaning “(in the) Year of the Phoenix,” was established at the start of 2017 to protest the world situation in the era of Donald J. Trump and Brexit through selling T-shirts and other merchandise. The name is a reference to 2017, or its equivalent in the Chinese calendar, which is the Year of the Fire Rooster or Fire Bird. The phoenix is a symbol of rebirth, and particularly rebirth from a crisis situation, such as the one the liberal international order now seems to face.
Technically, “Anno Phoenicis” is the ablative case form, which is used in Latin to express dates (among other things), whereas the nominative form is “Annus Phoenicis.” The nominative form is generally used in isolation in Latin, but may sound more odd to English speakers, so the ablative was chosen here. Thus, the meaning is “in the Year of the Phoenix,” instead of “Year of the Phoenix.”