.pastDay{
    opacity: 0.4;
    pointer-events: none;
}
.pastDay td:before ,  td.pastDay:before{
    content:'';
    position:absolute;
    display:block;
    width:auto;
    height:auto;
    left:0;
    top:0;
    right:0;
    bottom:0;
    background: rgba(0,0,0,0) url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' stroke='rgba(255,0,0,.9)' stroke-width='1.5'%3e%3cline x2='100%25' y2='100%25'/%3e%3cline y1='100%25' x2='100%25'/%3e%3c/svg%3e") no-repeat;
    background-size:100% 100%; 
}