I completely agree with everyone using UTC for numeric time numbering.
I DISAGREE, with remapping 'noon', 'midnight', 'morning', etc. All of the relative descriptions for when in the local solar day a thing is should be approximate local references.
An example: 'lunch' and 'noon' would still be the time in the middle of the local solar day that people get a meal. (Somewhere around 11AM to 2PM in current local times)