Fix time zone in wxDateTime::UNow().

The internal wxDateTime representation is in the UTC, so use
wxGetUTCTimeMillis() in UNow(), using wxGetLocalTimeMillis() made it
inconsistent with Now() and wrong.

Really closes #13862.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70418 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/datetime.cpp

@@ -1102,7 +1102,7 @@ wxDateTime wxDateTime::GetEndDST(int year, Country country)
 // return the current time with ms precision
 /* static */ wxDateTime wxDateTime::UNow()
 {
-    return wxDateTime(wxGetLocalTimeMillis());
+    return wxDateTime(wxGetUTCTimeMillis());
 }
 
 // the values in the tm structure contain the local time