When outputting datetime property from a custom data type using Excel Write component, the resulting cell in Excel worksheet is in General format.
This did work properly in previous Workflow versions. For example, Datetime of Aug 5 2014 11:47:11 will result in the cell on Excel worksheet displaying 41856. This field would be expected to be formatted as a date. In previous Workflow versions same cell has (custom) date formatting, cell content is shown as 08.05.2014 (and content being 5.08.2014 13:12:00).
Office components were updated in Workflow 7.5 SP1.
Symantec Development has created a fix for this issue. Please contact Symantec Technical Support to aquire the fix referencing article HOWTO101650. This article lists all available fixes for this version of Workflow.
Workflow 7.5 SP1
Note: This issue is not present in ServiceDesk 7.5 SP1 (as that is based on an older version of Workflow).