That answer isn’t easy to give.
If you look at an online newspaper or magazine, you will see that each new content must be published as soon as possible, because news have a short time of life. If it is a blog, normally is daily and it doesn’t need a specific schedule.
Although, when we talk about online video, it is a different thing. So, concerning online videos, is there any ideal time to upload them? Everything depends on the content that you are creating. Planning a schedule is something important to build an audience.
According to some sources, the best week day to publish content seems to be the Monday, especially in morning between 8 and 11am. The worst time of the day to publish new content is between midnight and 6am. At weekends, best time is early to mid-morning.
Therefore, if you want to reach a bigger audience, it is better to make a previous plan and study before you publish an online video.