Merge pull request #8856 from piwik/dateformats

core/Date.php

core/Period.php

core/Period/Day.php

core/Period/Month.php

core/Period/Range.php

core/Period/Week.php

core/Period/Year.php

core/Plugin/Visualization.php

plugins/Annotations/Controller.php

...nts.getContentNames_lastN__API.getProcessedReport_day.xml

...ts.getContentPieces_lastN__API.getProcessedReport_day.xml

plugins/CoreHome/CoreHome.php

plugins/CoreHome/javascripts/calendar.js

plugins/CoreHome/javascripts/donate.js

plugins/CoreHome/lang/ar.json

plugins/CoreHome/lang/bg.json

plugins/CoreHome/lang/ca.json

plugins/CoreHome/lang/cs.json

plugins/CoreHome/lang/da.json

plugins/CoreHome/lang/de.json