For the first time in history, and likely the last, the first day of Hannukah falls on Thanksgiving. According to Livescience:

By Tia Ghose, Staff Writer
It’s a once in more than 70,000-year event: The first day of Hanukkah this year coincides with Thanksgiving.
As a result, Jews everywhere are gearing up for “Thanksgivukkah,” a mashup of Thanksgiving and the Jewish festival of lights. This lineup of the first day of Hanukkah with Thanksgiving is incredibly rare.
“That’s not going to happen again for thousands and thousands of years. No one knows exactly how long, because the calendars aren’t going up that high,” said Jason Miller, a rabbi in Michigan who blogs at rabbijason.com. “It’s something like 70,000 years,” assuming of course that America, the Jews and the human race are still around at that time.

If memory serves me right, the last time this happened, turkeys were still dinosaurs. Fire hadn’t even been discovered yet, so they couldn’t be cooked anyway; Jewish Neanderthals could only fantasize about latkes. We’ve come a long way since then.
The article goes on to explain:

Many calendars
The reason for this year’s rare alignment has to do with quirks of two calendars, the Gregorian and Jewish calendars. Much of the world follows the Gregorian calendar, which has a 365-day year based on the Earth’s orbit around the sun, with leap years every four years. The Gregorian calendar was implemented by Pope Gregory to keep Easter in line with the season it was originally celebrated in.

But the Jewish calendar, which was created more than 2,000 years ago, follows the waxing and waning of the moon. That calendar has 12 months of roughly 30 days each, which works out to a bit more than 354 days in a year. As a result, the Jewish year creeps earlier and earlier relative to the Gregorian calendar. But many Jewish holidays, such as Passover, are tied to seasons such as spring.
To keep holidays in line with their seasons, the Jewish calendar includes an entire extra month in seven of every 19 years. This year is a leap year, so Hanukkah and all of the other Jewish holidays came especially early in 2013. And Thanksgiving, which falls on the fourth Thursday in November, happened to come extra late this year, allowing for the convergence.
Because the extra month on the Jewish calendar will occur in 2014, Hanukkah will once again happen in December, Miller said.
“That also allows us to get Passover back in the spring,” Miller told LiveScience.

In reality, the Jewish calendar was implemented out of necessity. In days of yore, the Jewish court (Sandhedrin) would wait for witnesses to come forward, each month, to testify that they had seen the new moon. At that point, the court would declare a new month and word was sent out to all corners of Jewish habitation. As for the extra month required to keep the holidays in season, Jewfaq explains:

In ancient times, this month was added by observation: the Sanhedrin observed the conditions of the weather, the crops and the livestock, and if these were not sufficiently advanced to be considered “spring,” then the Sanhedrin inserted an additional month into the calendar to make sure that Pesach (Passover) would occur in the spring (it is, after all, referred to in the Torah as Chag he-Aviv, the Festival of Spring!).

Why did ancient Jews stop using witnesses to declare the new month? It was because of diversity. All was well as long as the Jewish population was homogenous and unified. But after the Babylonian Exile, when full-blooded Jews came into contact with the half-bloods (Samaritans) who had settled in the Land of Israel, tensions flared. From the Center for Online Jewish Studies:

The Samaritans were a mixed people, made up of Israelites who had not been exiled when the Northern Kingdom was destroyed in 722 B.C.E. and people of various foreign nationalities whom the Assyrians had resettled in the area in an attempt to ensure that Israel’s national aspirations could not again come to the fore. This mixed group had adopted a syncretistic form of Judaism that combined old northern traditions with those of the resettled nations. When work began on the Temple, the Samaritans approached the Jews to join in the project. The Judeans rejected the Samaritans because of their questionable descent.
In First Temple times it was possible for foreigners to join the Jewish people in an informal way by moving physically and socially into the land and adhering to its religion and laws. During the exile, Judaism had been transformed from a nationality which depended on a connection to the land and culture to a religious and ethnic community which depended upon descent. How else could Judaism have ensured its continuity when deprived of its homeland? The returning Jews from Babylonia could not accept the questionable genealogy of the Samaritans. On the other hand, there was not yet a system for religious conversion like that developed somewhat later on in the Second Temple period. Hence, there was no choice but to reject the Samaritans, even had they agreed to abandon their syncretistic practices. In response to their rejection, the Samaritans attempted, although with limited success, to influence the Persian authorities to halt the rebuilding of the Temple and to limit the powers of the priestly and temporal government of the Jews.

The Samaritans used various tricks in order to sabotage traditional Jewish life. One of them is described by My Jewish Learning:

Originally, there was not a set calendar for Jewish months. Instead, the Sanhedrin would declare a new month after receiving the testimony of two reliable witnesses reporting that they had seen the new moon. Then the message was spread throughout Israel and Babylonia via small fires on hilltops. When a new moon was announced, someone would go to the top of the Mount of Olives in Jerusalem with a long pole of wood. He would set the end of his pole on fire and wave it around until he could see someone on another hilltop waving his own pole. The second person waved his pole until he could see a third person waving, and so on until the message reached Babylonia.
Eventually the Samaritans began lighting fires on hilltops in order to mislead the Jews, and so instead of fires, messengers were sent out from Jerusalem. By the later Amoraic period, a fixed calendar was set, and there was no longer any need for witnesses or messengers.

Due to the increased area of Jewish settlement, it became impractical to continue sending messengers in this way. The system of fires, had it not been abandoned, might have continued to function, at least for a while.
At first glance, having a calendar is a great convenience. It takes away the guessing game, removes the potential for abuse and allows people to plan ahead. On the other hand, something important was lost: There was no longer an intimate connection between the rabbinical authorities (the Sanhendrin) and the people. The institution of a calendar was a major step downward into the abyss of rigid ritual. It helped transform the Jewish people from a people of trust to a people of codification. The calendar was one of the first stages in the ossification of warm flesh and blood. No longer did people have to meet face to face in order to set the pace of national life. Now, all one had to do was consult the calendar.
Hanukkah is the anti-diversity Holiday. Hellenized Syrians had defiled the Temple and were attempting to stamp out Judaism among the Jews. The traditional story of Hanukkah, as it appears in Wikipedia, reads:

When the Second Temple in Jerusalem was looted and services stopped, Judaism was outlawed. In 167 BCE Antiochus ordered an altar to Zeus erected in the Temple. He banned brit milah (circumcision) and ordered pigs to be sacrificed at the altar of the temple (the sacrifice of pigs to the Greek gods was standard ritual practice in the Ancient Greek religion).^[17]
Antiochus’s actions provoked a large-scale revolt. Mattityahu, a Jewish priest, and his five sons Jochanan, Simeon, Eleazar, Jonathan, and Judah led a rebellion against Antiochus. Judah became known as Yehuda HaMakabi (“Judah the Hammer”). By 166 BCE Mattathias had died, and Judah took his place as leader. By 165 BCE the Jewish revolt against the Seleucid monarchy was successful. The Temple was liberated and rededicated. The festival of Hanukkah was instituted to celebrate this event.^[18] Judah ordered the Temple to be cleansed, a new altar to be built in place of the polluted one and new holy vessels to be made. According to the Talmud, unadulterated and undefiled pure olive oil with the seal of the kohen gadol (high priest) was needed for the menorah in the Temple, which was required to burn throughout the night every night…

The oil needed to be pure, the Temple needed to be purified and the nation needed to be purged of the cultural imperialism that had tainted it. Of course, all this is relative; there is no such thing as a “pure culture” and, as a matter of fact, they even could have used olive oil that was less than pure. But the concept behind Hanukkah is to take back the culture that is ours, that our enemies would extinguish if given the chance.
Perhaps it’s time that America had it’s own Hanukkah.