From the passage provided, what year did the Covenant attack?

Nearly a hundred thousand years later in the 26th century, humanity—under the auspices of the United Nations Space Command, or UNSC—colonized many worlds thanks to the development of faster-than-light "slipstream space" (i.e. hyperspace) travel. Tensions between the government and colonies desiring independence sparked violent clashes. The UNSC sponsored the SPARTAN-II Project to create an elite group of enhanced supersoldiers to suppress the rebellions covertly. In the year 2525, human worlds come under attack by a theocratic alliance of alien races known as the Covenant, whose leadership declared humanity heretics and an affront to their gods—the Forerunners. The Covenant began a genocidal holy war. Their superior technology and numbers proved decisive advantages; though effective, the Spartans were too few in number to turn the tide of battle in humanity's favor. After the Covenant invaded Reach, the UNSC's last major stronghold besides Earth, Master Chief John-117 was left as one of the few remaining Spartans.

The Covenant attacked in the year 2525.