Where it shows to be accepted on such date, the bar above it was half way blue for 3 weeks and then all of a sudden it went all blue all the way across. What does that mean exactly?

Mines the same way ! Don’t know what it means either 

The blue bar was half full, now it's all full.

Most likely, it's because you had an estimated date for your refund of 2/21/2020 and we have reached that date.  That information is not very accurate because it is just an estimate based on the fact that most, but not all, refunds are issued within 21 days of the Tax Return being Accepted by the IRS.  The only way to accurately track the date you will receive your refund is by visiting the IRS website for Where's my Refund.   If you see that your refund is Processing, or Still Processing, that's great....it means that the IRS is working on your return and hopefully you will have an Approved status soon.