Start with the production side
Official anime sites, publisher accounts, production committees, and licensed streaming newsrooms are the strongest first stop. A repost should point back to one of them.
Separate four different claims
A production announcement, Japanese TV date, international license, and exact streaming day are not interchangeable. Verify each claim independently.
Watch for changed plans
Delays are common enough that an old poster is not proof. Check the publication date and look for a newer official update before sharing a calendar entry.