Issue : Setting 'firstDayOfWeek' is Disturbing dates

[rabiasultankhan91]

https://user-images.githubusercontent.com/56686440/67014986-3820fc00-f10f-11e9-89de-fcdcaba28803.png

Hi
I have attached above the screenshot for reference.

I have made some customization in this plugin and attached screenshot is showing week Period view that means i can select weeks. One whole week is selected upon clicking any row of calendar.
Now,
I had my requirement to set the first day of week according to configuration. Lets say if First day of week is Monday then it should appear as first day and date should be accordingly adjusted. I am facing this issue that week days are rotated correctly but the date is not rotating.

For Eg. 29th Sept is appearing under Monday but it should appear under Sunday. How can I fix this Issue ?

Thanks