.unical {
    position:relative;
}

.unical .day {
    display:inline-block;
    margin:5px;
    background:#ddd;
}
.unical .day:before {
    height:0;
    width:100%;
    padding-bottom:100%;
    content:" ";
    font-size:0;
    display:block;
}

.unical.col10 .day {
    width:calc(10% - 10px);
}
.unical.col5 .day {
    width:calc(20% - 10px);
}