You will have to contend with all three Endbringers at once right as you arrive. You might have an hour or so of grace since the Endbringers will need some time to get to your location. Use your preparation time wisely.
If the Endbringers do not exist in the world you are in, several attacks will happen in quick succession starting a week after your arrival instead.
(If you picked Corona Pollentia, don't. You will die a horrible horrible death)