You can define your project specific Time Zone at the creation of your project. Each workday start and end time is calculated based on this setting. An item creation and completion date will record time according to project timestamp. This timezone selection will reflect on your project graphs as well.

The default Time Zone is GMT Western Europe Time. You can change the default Time Zone from Project Settings afterward. Change in Project Time Zone will reflect only in later item updates.

If your project team members are working in different time belts, decide your project timezone with your team. A user can change its personal timezone in profile settings that will reflect the time in respective user boards only. All item dates and graphs are still populated with project timezone settings.

Note: Daylight saving is not catered by project based Time Zones.

To know a Project Time Zone setting:

Go to Navigation menu, Settings > Project & Users > Manage Projects > Locate the Project > Settings > General Settings > Project Time Zone