Chanukka has eight days, the first light, the second light, et cetera, until the eighth light. They point to one date, one that is mentioned in the prophecy of Chagai. This is day zero of Chanukka, and is the day that Moshiach will be revealed to all.
"The word of HaShem came to Chaggai a second time on the twenty-fourth of the month, as follows. Speak to Zerubavel, ruler of Yehudah, saying:
I am shaking the heavens and the earth. I will upset the thrones of kingdoms and destroy the strength of kingdoms of the nations; I will turn over a chariot and its drivers, and horses and their drivers will fall down, one by the sword of the other. On that day, the word of HaShem, the Master of Legions, I will take you, Zerubavel ben Shealtiel, my servant, the word of HaShem, and I will make you like [My] signet ring, for you I have chosen, the word of HaShem, Master of Legions."
As we have the Shamash, we can express day zero of Chanukkah.
On the 24th of Kislev, we should therefore light only the Shamash, without any Berachah. If someone asks what this light is, we should simply answer "זה זכר לגלוי המשיח".
