YouTubs own analytics tool appears to be able to analyse things down to which "day" is best (using the filter "last week", you can see what day had the most views), but it doesn't break it down to the "hour". As mentioned, the TubeBuddy tool helps analyse your traffic and determines your best day and time of the week to upload based on when you get the most traffic to your videos. I feel TubeBuddy is sort of a required tool if you're serious about looking for ways to optimize your channel in ways other than looking at your content itself. I always post on Sundays because I work on my videos Fridays/Saturdays and that's working for me fine. Nevertheless, TubeBuddy suggested to me that I should be posting Thursdays at 4pm. Go figure