(Capcom's primary storyline)
Daylight was developed by Peter at Greg's behest. Peter believed that Greg would use it to safely expose the Umbrella Corporation's experiments to the public, but in reality, Greg was planning to use it as leverage against the company.
Peter created a simple recipe for the vaccine: V-Poison (from mutated wasps), T-Blood (from a creature infected by the T-virus), and finally, P-Base (a chemical compound requiring careful storage and mixing). When placed in a special incubator, the vaccine will be generated automatically. The Daylight is shown as a bright white liquid, when it is fully prepared.
Always poetically minded, Peter named the vaccine "Daylight," because "You don't need an Umbrella in the Daylight."
At some point prior to the G-Virus Seizure Operation's release of the t-Virus into Raccoon City's sewers, Peter learned of Greg's true motives. Although he got a message out to his long time friend, George Hamilton, by the time the doctor could get to the University, Peter had already been killed by a gunshot wound to the head as he sat at his desk.
Although dead, Peter still aided his old friend and his companions in the form of research notes scattered throughout the facility. Their survival hinged upon obtaining Daylight, becoming cured of the virus, and escaping the doomed city before it was wiped out by a missile strike.
Daylight was relatively well known in 2012, even after the WilPharma's more-recent "t-Vaccine" was mass-produced in 2005, possibly because t-Vaccine stopped producing when it was bankrupt and purchased by Tricell. It was suggested by Professor Doug Wright that the Marhawa School have access to Daylight, after discovering a schoolgirl he believed to be suffering from t-Virus infection.