PHOT is not heavily split in the current catalog, but the short label still hides the underlying IANA zone and any future policy change. The safe pattern is to write the abbreviation for humans and the zone for machines.
PHOT is a Kiribati/Phoenix Islands label at UTC+13; the legal-time issue is usually the local date as much as the hour. Not the same as Fiji, Nauru, Tonga, or New Zealand daylight labels: PHOT is a Kiribati island-clock context, not a generic Pacific +13 answer.
Pacific/Kanton sits at one of the far edges of the offset spectrum (+13:00). Pages and software that assume "close to UTC" often render PHOT incorrectly, so explicit handling is more important here than on UTC-adjacent zones.
For precise work, the safest equivalent of PHOT is the exact IANA zone used by your city or system. Pacific/Kanton sits at +13:00, ahead of UTC, which means daily logs in this zone reach a new calendar date before UTC does — a small detail that breaks date-based reporting if missed.
Within this single zone (Pacific/Kanton, +13:00), PHOT is unambiguous, so the abbreviation and the IANA zone effectively interchange.