Photo Time-Zone estimator

The result is an offset, not a zone: no IANA database is consulted, and a zone name would be a guess. Without a GPS timestamp nothing can be measured, because a camera clock alone carries no timezone. A corrected time when the offset tag is missing assumes the camera clock itself was right, which is the best the two remaining clocks can support. The solar offset from longitude is an indication only; real solar time also depends on the date and the equation of time.