To fix this, you have two options:
1) Go to to Settings > Global Settings.
2) Go to Default Preferences Tab.
3) Ensure that the Time Zone Region is UTC.
4) Run any activity report. You should be able to see the report
5) Go again to the Global Settings Preferences and put back the original regional settings.
NOTE: if the users already have customized their own Preferences, they will have to change manually their time zone region.
1) Click on your user name that is next to System Info (on the top at the right).
2) Go to Preferences and select the UTC Time Zone Region.
3) Run any activity report. You should be able to see the report.
4) Go again to your Preferences and put back the original regional settings.
5) Try again to run the report.