function setHeader()
{

	var today = new Date();
	var year = today.getFullYear();
	var nextyear = today.getFullYear()+1;

// today.setDate(today.getDate()) //check spring
// today.setDate(today.getDate()+90) //check summer
// today.setDate(today.getDate()+180) //check autumn
// today.setDate(today.getDate()+270) //check winter


	var season ='http://www.andertonbosonnet.co.uk/seasons/ab-grass.jpg';
	var headerImage = document.getElementById("ab-grass");

var tSpringStart=new Date();
var tSummerStart=new Date();
var tAutumnStart=new Date();
var tWinterStart=new Date();
var tNextSpringStart=new Date();

	tSpringStart.setFullYear(year,1,21);
	tSummerStart.setFullYear(year,4,21);
	tAutumnStart.setFullYear(year,7,21);
	tWinterStart.setFullYear(year,10,21);
	tNextSpringStart.setFullYear(nextyear,2,21);

	if ((today >= tSpringStart) && (today < tSummerStart)){ season = 'http://www.andertonbosonnet.co.uk/seasons/ab-grass-spring.jpg'};
	if (today >= tSummerStart && today < tAutumnStart) season = 'http://www.andertonbosonnet.co.uk/seasons/ab-grass-summer.jpg';
	if (today >= tAutumnStart && today < tWinterStart) season = 'http://www.andertonbosonnet.co.uk/seasons/ab-grass-autumn.jpg';
	if (today >= tWinterStart && today < tNextSpringStart) season = 'http://www.andertonbosonnet.co.uk/seasons/ab-grass-winter.jpg';
	
	headerImage.src = season;

}