There is no single best hour
Charts that say "post on Thursday at 2pm" are describing someone else's audience, often in one country and one niche, sometimes from a year the platform has already changed. Your viewers are not that chart. A gaming channel in one timezone and a gardening channel in another should not share a clock.
Use YouTube Studio for viewers, not for guesses
In YouTube Studio, open Analytics → Audience. The "When your viewers are on YouTube" report shows days and hours for the people who already watch you. That is the closest thing to a best time, and it is private to your channel. A public tool cannot see it.
Pick two or three of those hours and publish then, in the timezone Studio is showing (you can change it in the report). Give a new video a couple of hours before your audience is most active if you want the upload to be processed and the notification to land while people are around. Do not rebuild your week around a 30-minute window.
Publish time is not the same as viewer time
The timestamp on a public video is when it went public. It says nothing about who was watching. If you schedule uploads for Sunday because that is when you edit, the public history will say Sunday even if your viewers show up on Tuesday night.
The free upload-time tool on this site reads those public timestamps and plots them in UTC. Use it to see your own habit. Use Studio to see your audience. If they disagree, trust Studio and shift the schedule toward the audience, on days you can still edit.
Consistency beats a perfect slot
Small channels grow when viewers learn there will be another video. A stable weekday is easier to remember than a theoretically perfect hour you miss. Look at the last month. If you already publish on Tuesdays and Fridays, plan the next month on Tuesdays and Fridays and only then nudge the hour toward the Studio report.
Scheduling is fine. The audience cares when the video is public, not when you clicked upload. Premieres are a separate choice: they ask people to wait, so use them when you have a reason to, not as a default.
What else matters more than the clock
A clear title, a thumbnail that matches it, and a video that pays off the click change results more than moving an upload by an hour. If views are flat, audit the packaging of the last uploads before you blame the timestamp.