Ever round a corner straight into a blinding, low Sun? This works out exactly how high the Sun sits above the horizon, which direction it's in, and how much windshield-glare risk that angle carries, for any place and time you pick.
🌌 Where it is in the sky
Sun position comes from the standard NOAA solar-position equations: your date and time (converted to UTC using the time zone offset you pick) give a Julian day, which drives the Sun's ecliptic longitude, declination, and the equation of time (the few minutes a sundial and a clock disagree by, since Earth's orbit isn't a perfect circle). Combined with your latitude and longitude, that gives the Sun's hour angle, and from it, elevation and compass azimuth. A small atmospheric-refraction correction (Meeus, 1998) is added near the horizon, since the atmosphere bends sunlight enough to make the Sun visible for a few minutes after it's geometrically already below the horizon.
Glare risk up here is a rough read on elevation alone: the lower the Sun, the more likely it's sitting right at windshield height. It doesn't yet know which direction you're driving; the simulator below adds that.
This tool assumes a clear sky and doesn't check whether the Sun is actually above the horizon at your chosen time; if you pick a time before sunrise or after sunset, it'll say so. ZIP code lookup (US only) uses zippopotam.us to convert a ZIP into coordinates. The time zone offset is picked from a list rather than detected automatically, since a location's real offset depends on local law (including daylight saving), which isn't derivable from coordinates alone.
Spin the dial to the direction you're driving and see whether the Sun would actually be in your eyes.
A heuristic, not a ray-traced windshield: it combines how closely your heading points at the Sun's compass direction with how low the Sun is, and ignores seating position, window tint, and visor angle.