Whenever you are accessing your submissions via the Submissions Manager you will notice that there is always a Submission Created column on the left hand side:

Additionally, on WebForms there is a time stamp in the top right corner that shows when the form was submitted:

The following screenshots are for if you are on the updated layout for GovOS Studio. You will know if you are if you see a drop down for Account next to the Create button in the top right. If instead you see your username, then you are not on GovOS Studio 2.0.
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Both of these can be changed by the author of the form by going to the Forms Manager (page when you first log-in) and clicking on your username in the top right and then clicking on Profile:

Once you are in your profile there will be a section where you can change your Time Zone for all submissions on the form you are the author of:

NOTE: As mentioned above, only the Time Zone selected in the profile of the Author of the form will reflect in the Submissions Manager and on the completed PDF of a WebForm.
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