I could visit the website anywhere between 6am and 10pm, but the website is always busy at all hours of the day.

That's because it is an international website. My timezone is completely different to yours, so if I were to say I'm online at 4pm, it's a bit meaningless, because you might be asleep at 2am your time (for example).

If everyone answers this question with a time and their timezone, we'd be able to figure out the relative differences in time and see when the site is actually most busy in real time. Otherwise the responses here will just tell you when individuals like to use the site, so people's favourite time of day for them,   which is interesting, but it wouldn't tell you "which hours get the most visitors" which requires timezones to know the real answer.

I am at GMT+10  /   UTC+10

P.S. for student/teacher communication and lesson scheduling,  italki converts timezones automatically for each person so that each person sees things in their local timezone that they understand. It works really well and saves a lot of confusion. When you are dealing with written text (or speech) though, you have to be careful that when someone writes they will be online at 6pm, that might actually be a completely different time to your 6pm.