Main effect:
The probability is PP/65536.
PP is equal to 08 by default.
You can now put the value 10 (16 chances in 65536), like in Gen VI.
Decompress arm9.bin.
Go to offset 0×70080* and change the value 08 into QQ.
QQ can take any value from 00 (no shiny at all) to FF (roughly 1 in 257 chance).
*Regions' differences:
Language Shiny chance
Japanese 0×6FAC0
Spanish HG 0×70078
Korean HG 0×7017C
Korean SS 0×70174
Others 0×70080
Side-effect:
Formula reminder: (Trainer ID ⊕ Secret ID) ⊕ (16 leftmost bits of PID ⊕ 16 rightmost bits of PID) = CID
What I call the CID (stands for Color ID) must be a number between 0 and 7 included for its bearer to be shiny.
For example let's say you decided to update the value from 0×08 to 0×10, what will happen you may ask?
Any caught Pokémon who happens to have their CID between 8 and 15 included and who weren't shiny before the update will turn shiny!
When:
6/17/17 - 6/25/17 Receive Mallow's Steenee
6/26/17 - 7/04/17 Receive Kiawe's Turtonator
7/05/17 - 7/14/17 Receive Lillie's Alolan Vulpix "Shiron"
Where:
Several Aeon Malls in Japan:
http://www.pokemon.co.jp/images/info/2017/06/170609_gm01.pdf
How:
Bring your gaming device along with a copy of Pokémon Sun or Moon. Your copy of the game must be updated to the latest version to receive this gift.
Connection to the internet is required to obtain this serial code event.
Source: pokemon.co.jp
It is new event forJune an July!! From June 17th to June 25th, you can get Mallow's Steenee. From June 26th to July 4th, you can get Kiawe's Turtonator, and from July 5th to July 14th, you can get Lillie's Alolan Vulpix.
http://www.pokemon.co.jp/info/2017/06/170609_gm01.html