When you create an external content type using SharePoint Designer and it involves Date Time fields, than one thing you would need to consider is how date time values are handled in external content type.
If you've just configured external list that has date time fields from SQL database, then you'll probably notice that date time values displayed in external list is not same as it is in sql table. The reason being external content types created using SharePoint designer have defined to treat date time values in UTC format.
You'll make that out when you export the BDC model and look at xml descriptors.
E.g. in SQL table
In SharePoint external list,
You'll notice that the timestamp is off. If you export the BDC model and open that up what you'll notice is:
What we need to do here is tell BDC model to interpret date time value in local format. You can do so by changing the NormalizedDateTime element like below:
- Delete the ECT from SharePoint Designer
- Import the bdcm file in BDC Service Application from SharePoint Central Administration