th.hdr-month {
	border-top: 1px solid gray;
	border-bottom: 1px solid gray;
	text-align: center;
	vertical-align: middle;
	white-space: nowrap;
	transform: rotate(-90deg);
}

th.hdr-month {
	max-width: 4ex;
	border-top: 1px solid gray;
	border-bottom: 1px solid gray;
	text-align: center;
	vertical-align: middle;
	white-space: nowrap;
	transform: rotate(-90deg);
}

th.hdr-month {
	width: 6ex;
	position: relative;
}
th.hdr-month .vt {
	display: block;
	position: absolute;
	left: 50%;
	top: 50%;
	transform: translateX(-50%) translateY(-50%) rotate(-90deg);
}