Function sitemap_getDateformat
Gets the dateformat for images and albums only.
		
		Package: plugins\seo
Author: Malte Müller (acrylian) based on the plugin by Jeppe Toustrup (Tenzer) http://github.com/Tenzer/zenphoto-sitemap and on contributions by timo, Blue Dragonfly and Francois Marechal (frankm)
Located at zp-extensions/sitemap-extended.php
	
	Author: Malte Müller (acrylian) based on the plugin by Jeppe Toustrup (Tenzer) http://github.com/Tenzer/zenphoto-sitemap and on contributions by timo, Blue Dragonfly and Francois Marechal (frankm)
Located at zp-extensions/sitemap-extended.php
object | 
		$obj | 
		image or album object | 
string | 
		$option | 
		"date" or "mtime". If "mtime" is discovered to be not set, the date values is taken instead so we don't get 1970-01-10 dates | 
			string
		 | 
		string |