全网变灰白

css：

html{filter: grayscale(100%);-moz-filter: grayscale(100%);-o-filter: grayscale(100%);-webkit-filter: grayscale(1)}

或者

js:

var myDate = new Date();
if(myDate.getDate()+0 == 3){
  $("html").css("filter","grayscale(100%)")
  $("html").css("-moz-filter","grayscale(100%)")
  $("html").css("-o-filter","grayscale(100%)")
  $("html").css("-webkit-filter","grayscale(1)")
}

3号变灰白