Mailparser has a timezone setting that reflects in the Received At and Processed At times in the app, but when sending this data in a webhook, we always send via UTC for compatibility reasons.
That said, Mailparser allows you to easily parse date fields from the body text (or headers) of your email. Once isolated, you can refine the date field with our Date Formatting feature.
This means you can rewrite something like "Thursday, 16th of April at 2 pm" into for example "2015-04-16 14:00:00". Most of the time you want to do this if you send your parsed data to another program and the other program needs to understand the date format. The fields for "Received At" and "Processed At" are already in such a "machine-readable" format.
You can also directly modify a timezone in the parsing engine with the format dates filter, once the date itself is isolated:
Zapier also offers a function to alter date fields:
If you download your data as an Excel file, you can alter the timezone directly inside Excel. Have a look to get an idea of how this works: http://answers.microsoft.com/en-us/office/forum/office_2003-excel/how-do-i-convert-gmt-to-local-time/b0d5733d-007d-4505-992f-2742780a3ef5