Edit in JSFiddle

/*Date Sprite */
.postdate {
position: relative;
width: 66px;
height: 60px;
float: left;
}
.month, .day, .year {
position: absolute;
text-indent: -1000em;
background-image: url(http://cdn3.wpbeginner.com/guestposts/todd-santoro-css-sprites/date_img.png);
background-repeat: no-repeat;
}
.month { top: 10px; left: 0; width: 33px; height: 30px;}
.day { top: 30px; left: 0; width: 33px; height: 30px;}
.year { bottom: 0; right: 13px; width: 20px; height: 60px;}
.m-01 { background-position: 0 0px;}
.m-02 { background-position: 0 -30px;}
.m-03 { background-position: 0 -62px;}
.m-04 { background-position: 0 -94px;}
.m-05 { background-position: 0 -125px;}
.m-06 { background-position: 0 -155px;}
.m-07 { background-position: 0 -185px;}
.m-08 { background-position: 0 -217px;}
.m-09 { background-position: 0 -248px;}
.m-10 { background-position: 0 -279px;}
.m-11 { background-position: 0 -310px;}
.m-12 { background-position: 0 -341px;}
.d-01 { background-position: -51px 0;}
.d-02 { background-position: -51px -27px;}
.d-03 { background-position: -51px -57px;}
.d-04 { background-position: -51px -91px;}
.d-05 { background-position: -51px -122px;}
.d-06 { background-position: -51px -151px;}
.d-07 { background-position: -51px -185px;}
.d-08 { background-position: -51px -214px;}
.d-09 { background-position: -51px -249px;}
.d-10 { background-position: -51px -275px;}
.d-11 { background-position: -51px -309px;}
.d-12 { background-position: -51px -338px;}
.d-13 { background-position: -51px -373px;}
.d-14 { background-position: -51px -404px;}
.d-15 { background-position: -51px -436px;}
.d-16 { background-position: -51px -462px;}
.d-17 { background-position: -100px -0px;}
.d-18 { background-position: -100px -27px;}
.d-19 { background-position: -100px -57px;}
.d-20 { background-position: -100px -91px;}
.d-21 { background-position: -100px -122px;}
.d-22 { background-position: -100px -151px;}
.d-23 { background-position: -100px -185px;}
.d-24 { background-position: -100px -214px;}
.d-25 { background-position: -100px -249px;}
.d-26 { background-position: -100px -275px;}
.d-27 { background-position: -100px -309px;}
.d-28 { background-position: -100px -338px;}
.d-29 { background-position: -100px -373px;}
.d-30 { background-position: -100px -404px;}
.d-31 { background-position: -100px -436;}
.y-2009 { background-position: -150px 0;}
.y-2010 { background-position: -150px -60px;}
.y-2011 { background-position: -150px -120px;}
.y-2012 { background-position: -150px -180;}
.y-2013 { background-position: -150px -240px;}
.y-2014 { background-position: -150px -300px;}