No, it is not legal to ride a motorcycle without a helmet at any time, including nighttime, in California. The state of California has specific helmet laws in place that require all motorcycle riders, regardless of the time of day, to wear a helmet that meets the minimum safety standards outlined by the Department of Transportation (DOT).
Under California Vehicle Code Section 27803, all motorcycle riders and passengers must wear a helmet that complies with the DOT standards. The helmet must be properly fastened with a chin strap while the motorcycle is in motion.
It's important to note that helmet laws can vary by state, so it's essential to familiarize yourself with the specific laws and regulations in your jurisdiction. However, wearing a helmet is strongly recommended for all motorcycle riders, as it provides crucial protection in the event of an accident and can greatly reduce the risk of head and brain injuries.