Publication date/time in the News XML Sitemap
In the News XML sitemap, we use the GMT date and time for your publication. This might cause confusion sometimes, but is exactly according to the specification. At the <publication_date> section the W3C site is linked, where it says:
"Times are expressed in UTC (Coordinated Universal Time), with a special UTC designator ("Z")."
There would be the other option of adding the date/time with a time zone designator, but we've found that's much more error prone. Since WordPress already saves the GMT date/time in the database it's actually also a lot easier from a development perspective.