Google is unhappy with thai calendar dates we currently have showing up in <time> tags on arwiki:
<time itemprop="startDate" datetime="2551-09-30T20:30:00+00:00" style="display:block;overflow:auto"><span class="mobile-float-reset" style="display:block;float:left">30-09-2551</span><span class="mobile-float-reset" style="display:block;clear:left;float:left">20:30</span></time>
The errors started on December 26:
I presume Google expects Gregorian dates instead in those HTML tags.