The UNSC Bright New Day was a Paris-Class Heavy Frigate, constructed in 2524. Though a fairly unremarkable ship with no special modifications, it seemed to possess an uncanny luck as it survived numerous engagements throughout the Human-Covenant War and returned to fight time and time again. Acting primarily as a support vessel for larger fleets, the Bright New Day was known for its surprising speed and endurance, and would help to oversee the evacuation of multiple worlds over the course of several decades. Constantly moving from fleet to fleet, the Bright New Day became somewhat famous as one of the longest-surviving ships during the war and had several captains, though it was eventually slated for decommissioning in mid-2552.
Before the ageing frigate could be taken apart, the Covenant attack on Reach left it abandoned and in storage close to the ship breaking yards in Asźod. As the planet fell to the enemy, a small Spartan-led force commandeered the Bright New Day and used it to escape the planet. The frigate would participate in several more battles over the course of the next few weeks, playing a pivotal role during the Battle of Second Sanctum before its crew finally returned to the Sol System. With many of its systems beginning to fail, the UNSC Bright New Day met its end in Earth's orbit, colliding with a Covenant cruiser while those on board escaped to the planet's surface.
During the initial assault on the planet in March of 2552, the Bright New Day was part of its token defence fleet, made up of one Halcyon-Class Cruiser, the UNSC Konakli, and two other frigates; the UNSC Troy, and the UNSC Starhood. The other three ships were destroyed in combat, forcing Captain Uriah Maxon to order a retreat to Harpa's surface. Unable to combat the superior Covenant force, Maxon used the Day as an emergency evacuation point for any remaining civilians and UNSC forces stranded on the planet. It would evade enemy patrols until March 14th, when the remnants of Harpa's defensive forces boarded the frigate. The ship would have abandoned many as Maxon wished to escape the system, but the Captain was convinced to wait by Spartan Fenn-145, who allowed him to rescue Jax-007 and a small ODST contingent before departing. As they left Harpa, the survivor-laden frigate was contacted by the Covenant super-destroyer, Justicar.
The enemy Shipmaster, Felo 'Ranakee spoke to the crew of the Day, and ordered them to give up navigation data that would lead the Covenant to the human homeworld in exchange for their lives. Unable to outrun or outfight their foe, the crew was left with few options until Fenn-145 opted to fool the Covenant into thinking that they would comply with their demands. Fenn and Lieutenant Martin Keel of the ODST's would sacrifice themselves by travelling into the super-destroyer under the pretence of delivering hard copies of navigational data, only to detonate several nuclear warheads and obliterate the massive ship from the inside. With any surviving Covenant troops trapped on Harpa, the Bright New Day was able to escape from the system, and would eventually travel to Reach.
After Captain Maxson was transferred into the Epsilon Eridani Defence Fleet, the Day was left leaderless for several months after it arrived at Reach. In July, the ageing vessel was slated for decommissioning and was taken to a storage bay close to the Aszod shipbreaking yards to be dismantled and destroyed. However, the planet was attacked, halting all work and leaving the ship manned only by a skeleton crew of technicians. On August 30th, the remnants of Spartan Teams Sigma, Tau and Upsilon arrived nearby, having failed to escape Reach via the UNSC Pillar of Autumn.
As one of the only spaceworthy vessels in the area, the ODST squad Whiskey-04 had also arrived while fleeing the Covenant and gave the order for it to take off as soon as possible. Fending off waves of Covenant aggressors, the Day's defenders soon linked up with the surviving Spartans and lifted off, narrowly avoiding the Covenant fleet that had begun to blockade the planet before making a randomised Slipspace jump to escape. Without the presence of a naval officer on board, Master Chief Petty Officer Kane-098 took command of the ship.
After picking up a distress signal from the colony world Hope, the Bright New Day travelled there, only to find it under attack by the Covenant. After a brief skirmish with a Covenant ship, the frigate's FTL drive was damaged, forcing it to land on Hope's surface. Sigma Team set out, leaving the ODST's and crew behind to take care of the ship, to find survivors and the materials needed for a repair. After a short battle in Port Neandra, and after ambushing a large Covenant patrol the Spartans were able to acquire an FTL drive from an undamaged ship stored in the Port Neandra Shipyards. The FTL drive and Sigma Team were airlifted by Sergeant Major Richard Mack Junior and his team. At this time, Hope began to fall apart. After a lengthy chase, they were able to make it back to the frigate and install the drive, giving them proper slipspace capabilities once more. With the planet crumbling around them, the Bright New Day was able to barely escape to the edge of the system as Hope imploded.
Shortly after Hope's implosion, the frigate was contacted by the UNSC Heavens Asunder, a stealth corvette under the command of Elena-071. Outranking the ship's rag-tag crew, Elena ordered the Bright New Day to follow the slipspace trail of a group of nearby UNSC ships to a newly-discovered Forerunner planet known as the Zenith Complex. Forced to act in secrecy, the crew did not contact their allies and deployed the Spartans to the planet while the frigate underwent further repairs in orbit, deploying its SPARTAN-III's shortly after to help combat Covenant forces on the ground while Whiskey-04 watched over the ship once more. Their time on the Zenith Complex was brief, however, as the Spartans soon recovered an artifact from its surface and returned it to Elena, who departed at once aboard her Prowler. Alone once again, the Bright New Day would continue its slow journey back towards Earth, heading for the nearest UNSC navigation point.
The frigate and its crew arrived back in the Sol Sytem on November 1st, 2552, only to find it under attack by a sizeable Covenant Fleet. With many of the Frigate's systems close to failing from age and accumulated battle damage, Kane-098 ordered the crew to abandon ship as it approached Earth. While most of the remaining crewmen and technicians used escape pods, the Spartans and troopers made use of orbital insertion pods to abandon ship after plotting the frigate on a collision course with a nearby Covenant cruiser that had been turning to attack it. While a volley of plasma fire critically damaged the unmanned warship, its speed paid off one last time as it smashed into the enemy vessel, destroying both ships in Earth's orbit and ending a lengthy service career for the Bright New Day.