The reporting job should be run from a server on UTC and on UTC time. The report itself can convert to whatever is local time. This is exactly what I said above.
All of yours might well be, but you can't generalize that assumption to every domain and scenario.
How are you going to do this? Clearly cron (with timezone set to UTC) doesn't work for this so you'll need another system. In that case why not have that multi-time zone scheduling system run your script?