At the day of The Chosen One's birth, the world is overjoyed. The sun shone brighter, yet the rays are warm instead of stinging hot, the wind is calming and the flowers blooms. The pokemon, in turn of the world's apparent good mood, are happy and content.
For the world followed the will of Arceus, and the Pokemon Deity is smiling as it observe The Chosen One.
(And then Arceus watched how the Chosen One, still a babe, was admitted to Emergency Room, flurry of Doctors yelling orders before an oxygen mask was put on his face along with cables on his small body; the small Chosen One was encased in a different room, encased with glass.
"... Life expectancy less than ten years."
"Forget ten years, if we can't handle this infection—" )
.
.
The day Ash Ketchum was born, right on the mid-day of bright, happy day, the sun was suddenly encased with gray clouds and a storm violently reigns over.
On the days to come, many professors would discuss this very abrupt, miraculous change, involving theories aorund Legenday Pokemons or simply natural disasters. They never found the definite answer though, dancing around various records of history and Legendaries, and eventually called it a day; they recorded the day as anomaly.
(Later, a very bewildered Zapdos would return to its nest looking at the various offerings littered around his island, but it supposes, it kinda deserves all of those after what has happened)