I thought I'd round out Star Wars week with a summary of the classic time periods available to Game Masters. The political and social landscape of the galaxy changes drastically as time progresses in the Star Wars Universe. Each provides unique opportunities for adventure. And while you may want to stick to what you're already familiar with (either from the films, or from books you've read) this list can help foster ideas about where you'd like to take your games as time progresses in your own little version of the Star Wars Universe. Or, perhaps, even give you an idea of which periods you'd like to look into further.
As with all Star Wars posts, this list focuses on the classic Star Wars trilogy and the fiction based on it, rather than anything based on the prequel films, which were bad. For those unaware, the Battle of Yavin (where the first Death Star is destroyed) is used as year zero. Dates are measured as either Before the Battle of Yavin (BBY) or After the Battle of Yavin (ABY).
Pre-Rebellion Imperial Era
From the establishment of Palpatine's New Order in 19 BBY, to the signing of the Corellian Treaty in 2 BBY
Most of the truly iconic imperial technology had not yet been deployed during this period. The Death Star was, obviously, still being designed and built. And ship types such as the Imperial Star Destroyer, and the Executor Class Star Destroyer (or "Super" Star Destroyer) were likewise still on the drawing table. Though some would have been under construction in secret shipyards owned by Kuat. The Emperor also humors the Imperial Senate, providing the illusion of representative government.
There is no organized resistance to the Empire. There are many dissident groups, but they are independent from one another, and easily crushed by the Empire. It isn't until two years prior to the Battle of Yavin that a group of Imperial Senators, in an act of treason, sign The Corellian Treaty, bringing the disparate rebel groups together to form The Rebel Alliance.
From the signing of the Corellian Treaty in 2 BBY, to the Battle of Endor in 4 ABY
Also known as the First Galactic Civil War, this period is probably the most well known, as it takes place primarily during the original trilogy of films. The Rebel Alliance and Empire engage in a brutal conflict. Many of the Empire's most notable atrocities and most terrifying weapons occur during this period: the destruction of Alderaan by the Death Star, and the creation of the Executor class Star Destroyer among them.
Early New Republic Era
From the Battle of Endor in 4 ABY, to the Conquest of Coruscant in 7 ABY
After the death of both Emperor Palpatine and Darth Vader at the Battle of Endor, the Galactic Empire is thrown into chaos. A whirlwind of successors hold the reigns of power for a short time, only to be assassinated or otherwise removed from power. Sometimes a single leader dominates, other times a small group will declare itself a ruling council of some kind. Meanwhile, more and more powerful Imperial leaders simply split off from the Empire, becoming Warlords.
In the days after the Battle of Endor, an interim government is formed by the Rebel Alliance, calling itself the Alliance of Free Planets. And one month after the battle of Endor, the Declaration of a New Republic is issued. Planets begin breaking off from the Empire immediately, joining the New Republic. Imperial responses to these "secessionists" is sporadic at best. Most of the New Republic still relies on secret bases, but the government makes itself visible. The New Republic continues to be viewed as a feeble government, in its infancy, until the conquest of Coruscant three years after the death of Palpatine.
New Republic Era
From the Conquest of Coruscant in 7 ABY, to the signing of the Pellaeon-Gavrisom Treaty in 19 ABY
The New Republic consistently grows in power, whilst the Empire becomes continually weaker. There are some brief periods of upheaval, in which the Empire surges and becomes a serious threat to the stability of the New Republic, such as the dreaded Thrawn Crisis, or the brief rule of the Reborn Emperor.
This is simultaneously one of the most and least varied periods in Star Wars history. On the one hand, the number of major events which occurred during this period are numerous and interesting. Yet when all is said and done, everything returned to more or less the status quo.
The Empire's territories steadily shrink during this period, until Fleet Admiral Gilad Pellaeon, as supreme commander of the Empire, with the backing of the Moff Council, signs the Pellaeon-Gavrisom treaty, ending the 21 year Galactic Civil War.
One other major event occurs during this period which will shape the fate of the galaxy through the future: Luke Skywalker establishes his Jedi Praxeum on Yavi IV in the year 11 ABY, officially beginning the training of a new generation of Jedi Knights.
Late New Republic Era
From the signing of the Pellaeon Gavrisom Treaty in 19 ABY to the start of the Yuuzhan Vong War in 25 ABY
Remarkably little has ever been written about this period. Primarily just the children's books and young adult novels written about the youthful adventures of Han and Leia's children and their friends. So aside from those relatively minor threats to galactic peace, these few years are a time of relative tranquility in the galaxy.
New Jedi Order Era
From the start of the Yuuzhan Vong War in 25 ABY with the First Battle of Helska, to the end of said war in 29 ABY with the Liberation of Coruscant.
The Yuuzhan Vong invade the galaxy, initiating one of the most brutal and bloody wars in galactic history. The Yuuzhan Vong's organic technology is, at first, completely invulnerable to any attempts to attack it. Thousands of worlds are conquered by this technology-hating species, and completely reformed to fit the needs of the Yuuzhan Vong. Trillions upon Trillions of beings are killed, and many completely loose hope that anyone can stand against the onslaught.
The New Republic has grown complacent and weak in the years since the treaty with the Empire, and is ill prepared to handle the invasion. It consistently makes major blunders, and eventually loses control of Coruscant to the invading Yuzzhan Vong hordes. After the death of Chief of State Borsk Fey'lya, along with much of the senate, Cal Omas was elected leader of the New Republic. And shortly after the New Republic victory at the Battle of Ebaq 9, it was decided that a new, more united government would be required if the war was to be won.
And so the New Republic was dissolved, and reformed as The Galactic Alliance, which also included the Imperial Remnant, as well as the Hapes Consortium. And, with the cooperation of the Chiss Ascendancy and the Jedi Order, the Galactic Alliance was able to push back the Yuuzhan Vong, defeat their war machine, and make peace with those who remained.
Galactic Alliance Era
From the Liberation of Coruscant in 29 ABY, to the blundered Operation Roundabout in 40 ABY, sparking the Second Galactic Civil War.
This is yet another period of relative calm, like the late New Republic era. The damage done during the Yuuzhan Vong war is never fully undone, but much effort is invested by the Galactic Alliance in trying to soothe the wounds of the war. Finding new homes for a planet's worth of refugees, and so forth.
Second Galactic Civil War Era
From Operation Roundabout in 40 ABY, to the Battle of Shedu Maad in 41 ABY
The planet Corellia begins to express a lack of satisfaction with Galactic Alliance rule, and talks of succession. The two governments posture at one another, until a series of blunders leads to an all out war between Corellia and the Galactic Alliance. Neither side has the moral high ground in this conflict. More than any war prior to it, the Second Galactic Civil War pits family members against one another.
Guided by Sith teachings, the grandson of Darth Vader, Jacen Solo, gradually assumes power over the Galactic Alliance, and takes the name Darth Caedus for himself. Under his leadership, the Galactic Alliance becomes as loathsome as Palpatine's empire before it. The Hapes Consortium withdraws from the Galactic Alliance, and the Jedi Order abandons it.
Darth Caedus is killed at the Battle of Shedu Maad by his sister. Natasi Daala is named Chief of State of the Galactic Alliance.