By default, the time zone in your workspace (project) is set to Pacific Standard Time (UTC -08:00). Insights in a workspace reflect time bucketing based on the current time in the workspace time zone.
Time Zones vs Reporting
The time zone setting can significantly affect reporting. Time zone settings affect how the platform determines "Today" and "Yesterday" that are used in the date filters.
For example, a user from Europe wants to receive an insight about yesterday's activities at 7 AM every morning, and the project time zone is set to default. If the insight is created with the "Date is Yesterday" filter, it would be calculated for the day before yesterday due to the time offset between Central European Time and Pacific Time. Therefore, from the system's point of view it is still the previous day, while for the user it is the next day already.
As needed, workspace administrators can modify the time zone for the workspace. For more information, see Setting a Custom Time Zone for Your Workspace.