Sunrise and sunset are generally the safest times to photograph the sun because the atmosphere greatly reduces visible light as well as much of the UV and IR. That said, there isn’t a precise in-camera test for “safe enough.”

For the camera: brief exposures through a DSLR’s normal shooting cycle are usually within expected use, since the sensor is only exposed during the shot. Live view is the bigger concern, because the sensor is exposed continuously, and some cameras specifically warn against using it when aimed at very bright light sources.

For your eyes: if you are using an optical viewfinder, remember you are looking through the lens, which concentrates light. Even if the sun appears dim to the naked eye, caution is still wise.

A practical rule: short, occasional shots of the sun at sunrise or sunset are usually fine; avoid prolonged live view or prolonged viewing through an optical viewfinder. If the sun is higher or much brighter, don’t risk it without proper solar filtration. A UV filter is not a safe solar filter, though UV is less of a concern specifically at sunset.