I think the author is talking about how ISO dates typically get converted and stored as integers or normalized (to UTC) ISO strings. If a payment was made in a

I think the author is talking about how ISO dates typically get converted and stored as integers or normalized (to UTC) ISO strings. If a payment was made in a different timezone from the server, the timezone locale (e.g. America/Los_Angeles) also needs to be separately stored in the db in order to preserve the full human readable meaning of the original payment date. If timezone offsets are separately stored (or the UTC normalized ISO strings), this still isn't sufficient to know which locale the offset is referring to since multiple locales use the same timezone offsets. It gets even more complicated when different locales shift their timezone offsets throughout the year due to daylight savings.