Curve clock

This uses d3.curveCatmullRom with four points, the centre of the clock, and the hour, minute and second points. It's got a pleasing smoothness a bit like a lava lamp.

<!DOCTYPE html>
<html>
<head>
	<title>Curve Clock</title>
</head>
<body>

.curve-clock {
		background: #fff;
		width: 100vw;
		height: 100vh;
	}

.curve-clock path {
		fill: none;
		mix-blend-mode: difference;
	}

</style>

var size = 1000
		var radius = size * 0.4

var tau = Math.PI * 2

var svg = d3.select('.curve-clock')
			.attr('viewBox', [0, 0, size, size])

svg = svg.append('g')
				.attr('transform', 'translate(' + [size/2, size/2] + ')')

var line = d3.radialLine()

var curve1 = svg.append('path').style('fill', '#c00')
		var curve2 = svg.append('path').style('fill', '#0c0')
		var curve3 = svg.append('path').style('fill', '#00c')

var r1 = Math.sqrt(0.9) * radius
		var r2 = Math.sqrt(0.6) * radius
		var r3 = Math.sqrt(0.3) * radius

function render(date) {
			var ms = date.getMilliseconds() / 1000,
				s = date.getSeconds() / 60,
				m = date.getMinutes() / 60,
				h = date.getHours() % 12 / 12

var data = [
				[0, 0],
				[tau * (s + ms / 60), r1],
				[tau * (m + s / 60 + (ms / 6000)), r2],
				[tau * (h + m / 12 + s / (12 * 60)), r3]
			]

curve1.datum(data).attr('d', line.curve(d3.curveCatmullRomClosed.alpha(0)))
			curve2.datum(data).attr('d', line.curve(d3.curveCatmullRomClosed.alpha(1)))
			curve3.datum(data).attr('d', line.curve(d3.curveCatmullRomClosed.alpha(1.5)))
		}

function tick() {
			var now = new Date()
			render(now)
		}

d3.timer(tick)

})()
</script>
</body>
</html>

https://d3js.org/d3.v4.min.js