That is another question related to social media marketing and online videos.
As in any media, online videos also have a prime time.
First you need to answer if your videos are for general use of the end consumer, like people watching from home or if it is to be watched by a business audience, during work hours.
Second you need to take into consideration where in the world the majority of your audience is and take into consideration the time frame there.
Prime time to post online videos:
For home audience: Between 4pm and 9pm
For a business audience: 7am to 9am, 11am to 1pm, 3pm to 5pm
You should avoid posting outside these frames