[Timeline] [dev branch] Major axis labels displaying wrong value

This is on the dev branch so I don't have a JSBin, but I do have screenshots.

The below screenshots are for http://visjs.org/examples/timeline/groups/groups.html

This is what it looks like on the website:

And this is what it looks like locally from dev:

Note the major axis (the bottom-left text "January 2017" and "00:00:00")

I did some digging and found that the issue stems from this commit: 9f0376ea Reverting the second change (the one for _repaintMajorText), makes the major axis act the same as it used to. @yotamberk, since this is your commit, would you know a nice fix for this?