DAY AS A THOUSAND YEARS. This passage cannot have a literal meaning, otherwise it would be nonsense. Thus, it cannot mean that a short time really means a long time. Jesus was in the tomb three days. Does that mean he was in the tomb three thousand years, and his resurrection is still a thousand years off?
The context of this statement in 2 Peter 3 is that the scoffers were reminding Peter that Jesus had promised to return in judgment in their generation, but now, about three decades later it had not yet happened. So, Peter scolds the scoffers and advised them that “The Lord is not slow to fulfill his promise” as they themselves were “waiting for the hastening day of the Lord” (2 Peter 3:12). So, Peter, writing in the early 60’s AD was issuing a strong warning about the soon coming destruction in AD 66-70 when Jerusalem was leveled by the Romans, the temple destroyed, and the system of temple ordinances ceased forever as the Old Covenant order was abolished. So, rather than arguing that the Fall of Jerusalem was a long time off, Peter was arguing that it would happen soon. And he was correct.
For more details about 2 Peter 3, see my articles in section B here:
https://prophecyquestions.com/2016/02/01/articles-by-charles-meek
Red herrings. The phrase pertains to prophecy.