Working in an environment that hosts servers offering SharePoint at a world wide level I see a common confusion in how SharePoint deals with time zones in relation to files.
Lets step through some examples, and then we can address it with a solution that is appropriate for your circumstance.
First thing to understand is how the SharePoint server stores your files. When you upload a file regardless of what time zone you are in SharePoint server stores it into the SQL database using the Co-ordinated Universal Time (UTC) time zone.
NOTE: Never change set server time or time zones of any server in your SharePoint farm.
I created an example file on the server desktop with the following date/time properties.
My server time zone is set to UTC. I then uploaded the file to SharePoint document library. When I uploaded the document 11 minutes later it reset the ‘created’ and ‘modified’ values. This happens regardless of the file type.
Using a handy tool called SharePoint Manager I was able to track the documents unique ID and file properties.
(This is a very useful tool which should be in your arsenal of SharePoint troubleshooting tools.)
I do not recommend directly viewing, or modifying, any of your SharePoint SQL databases.
Keep in mind SharePoint Manager uses the SharePoint API to pull all meta data. SharePoint Meta data is filtered, and set to SharePoint server settings. In the raw SQL content database we can verify that the file is stored in UTC time zone regardless of what ever time zones any server via this Microsoft article 184.108.40.206 AllUserData Table.
The implication here is that regardless of which time zone the file is uploaded the time zone data is reset and stored in UTC.
There are three different places you can change time zone settings depending on your need. I’ll start from the highest SharePoint server setting to the client setting.
Web App Level
The first is top level web application level set from the SharePoint Central Admin. The default as we can see there is that no time zone it set.
When the setting is blank the time zone is set to what ever the time zone of the server is set. When applying the time zone setting at the web application level this applies this will make a default setting to all site collections that are within this web application. Generally I would only recommend setting this if you are confident that all of your SharePoint users will be in the same time zone. Remember that this only the default, and can be changed at the site collection or user level.
Site Collection Level
The second level working downward is to set the default time zone at the individual site collection. This is a more common time zone setting to set for your SharePoint site. You will want to set the time zone where majority of your users will be physically located.
Site Actions>Site Settings>Site Administration>Regional Settings
There will be several other settings that can be set at this level for the SharePoint site collection and SharePoint users. You will need to be at least a site collection administrator to make this change. As before these default level can be over-ridden at lower user level.
The last and lowest level will be at the SharePoint user level. Looking at my SharePoint site from my workstation I can see the following.
While my workstation is set to the Central Time zone the SharePoint Client is still set to the default UTC time zone. It is important to note that if you open the same document library using the ‘Explorer View’ that the time are then translated to your workstation’s set time zone.
To set your SharePoint user level time zone
Your Name on the upper right hand side>My Settings> My Regional Settings
From there you can set user time zone settings for the user level. This will then correct the time zone discrepancy.