Share your launch on your social media (indiehackers, twitter, linkedin...) and contact your Asian and European connections first, as they will be the only ones awake on launch time, and then get ready to answer every comment and DM as fast as you can, be available for the people interested or curious about your product
I'd block the day off, and spend all of it talking with people in the comments, or on Twitter about the launch. Think of new places and communities you can share it in, and make sure your audience and users are engaged on launch day.
We have a checklist with what to do before, on, and after launch day that might help: https://taskablehq.com/templates...
PH launch day will be very busy, prepare in advance for the obvious things like FAQ's, materials, people and allocate proper time for each. prepare a to-do list with the team, you can use Poppins on slack for that and assign tasks to individuls.