Is night sky getting brighter day by day? Night sky is dark because light from distant stars has yet not reached our earth. Light emitted by stars formed after the instant of creation i.e. 13.7 billion light years ago is on the way to reach us. As light from these distant stars reach us, night sky must keep getting brighter.
How true is this? And to what extent? Can one day night sky become as bright as a day?
The rate of star formation in the universe peaked about 3.5 billion years after the Big Bang, or 2.7 billion years after it, according to a different study—in any case, for most of the universe's lifetime fewer and fewer stars have been forming each year. Though I don't have precise data on the death rate, on the whole the number of stars is decreasing as more old stars die than new ones form.

Meanwhile, the light from old stars is being redshifted out of existence by the expansion of the universe, which is itself accelerating.

I'm sure there's a mathematical model that can quantify this properly, but I think those two facts, combined, must be the answer to why the sky isn't getting brighter.