Date field displays the previous day after import

This is a common issue for organizations with users in multiple time zones, particularly around daylight saving time transitions.

When loading data into date fields such as Opportunity Close Date using the Data Loader, the date displayed in the application is sometimes one day earlier than the date in the file.

The reason for this is that fields such as Close Date are actually date/time fields.  When a date is loaded without specifying the time, the time is defaulted to 00:00 - midnight.  When another user is in a time zone which is behind the current user's time zone, the date will show on the previous day. 

For example:

20 August 2008 00:00 in Paris is 19 August 2008 23:00 in London

Similar issues can arise when daylight savings time begins or ends.