Hi Sayn,
Sorry for the late reply. Looking at the screenshot, I guess there is CSS from some other plugin injected in all WordPress admin page which breaks the calendar popup.
Since there is no known reported issue, I would need to access the page directly to find the RC of the issue.
To narrow down the issue yourself you can deactivate any newly installed plugin one by one and see if the issue resolves.
Please let me know how I can assist you in this matter. Menawhile please continue to enter the datetime manually.
Thanks,
Aakash
