What is golden hour?
Photographers call it golden hour because the sun is close to the horizon, the light travels through more of the atmosphere, and colours go warm. Shadows lengthen and faces are easier to light without a harsh overhead sun.
This site treats golden hour as the stretch when the sun’s centre is between 6° above the horizon and official sunrise or sunset. That matches a common field rule (roughly the last and first 30–50 minutes of sun at mid latitudes, shorter in the tropics, longer toward the poles). Other apps, including PhotoPills, sometimes start or end at a slightly different altitude, such as −4°. If you are matching another app, check which altitude they published.