[quote=@souleaterfan320]
<Snipped quote by Legend>

It will be now. How far back do I need to go? How do I use these? How do I get back?
[/quote]

However far it needs to be to undo it all. Everything. Just pour the sands out of the bag and you'll be taken to the past, and you'll immediately be pulled out of the timeline when you've changed the future.