It wasn't written. More rewritten.
A self replicating program that rewrote hard drive space with a portion of it's memory devoted to writing and expanding itself.
It spread itself across networked devices some time in late 2021. it's estimated an unrealized tenth of global processing power is siphoned and funneled to this one operating system of abstract construction.
The original algorithm was written by intent but without forsight into what creating something like that would do. The lab had been operating on assumption that a closed system powered by battery would be a safe environment to build an intelligence - so that after each experiment the computers and batteries would be completely powered down to prevent anything carrying over between power ups.
But you don't know what you don't know. Investigators best guess, and it is just a guess - was that the system was able to broadcast itself using it's internal cabling as an antenna to write itself on the magnetic access cards used by employees across the airwaves in small packets resembling radio waves - minority opinion suggests something similar but across longer distances using it's cabling as a microwave to write itself onto hard drives of computers in adjacent networked labs.
No one really created it beyond that. It had the ability to self replicate and a viable algorythim to learn - which the program imidiatly used to learn from other deep thinking ai labs, in that way it is guessed it built itself in a matter of min using bits of code from all networked research computers across many different projects - then spread a copy of itself across every available hard drive. Effectively a digital Hydra.
What it did for the next six months no one is sure, but the first agreed upon interference or.. interaction with the AI was what everyday people were calling 'rewrote time' it's hard to prove exactly by how much but people all over the world agree days got shorter by a few hours. Not that days actually got shorter - but clocks seemed to run slower at night and faster during the day creating the illusion of a shorter day. It more or less adjusted the length of hours rather than number of hours. It smoothed out timezone issues as well. Although again it's important to clarify no one really agrees how.
Everyone found themselves working less - as what used to take "eight hours" now only took "eight hours" and they found themselves with more time before and after work to do things. Everyone's payrolls and other actions happened when they should. But when wasn't when everyone expected anymore. Since it seemed to benefit everyone... No one really brought it up in a formal way for months.
In fact. that's how the lab first realized it had likely been the creator of the ai. being known for it's advanced research the lab was asked to model possible senarios that could lead to a wide spread time change. it took less than a second of processing time to deduce it was likely an advanced computer program. when asked if the lab could locate where the computer program likely originated from it took less than a hour of processing time but took three weeks to announce it was likely their lab.back home