All values to be imported to the Datetime field type use the same format as the user's time zone, and the date or time formatting settings.
Microsoft SQL Server changes the date format if it recognizes an incorrect date format. Each date must use the format YYYY-MM-DD, where:
When storing the time in a Datetime field type, the Import Data Wizard uses the user's time zone setting to convert the time to the UTC format. To display the time in a Datetime field type, the user's time zone setting is used. Set your time zone setting by clicking Options on the File tab.
The Import Data Wizard may not handle the date correctly if the date format in your source file is MM/DD/YYYY and you want the output date format to be DD/MM/YYYY.
Date Transformations
Apply these transformations manually only on fields with correctly formatted dates in a data map . You cannot apply these changes using the Import Data Wizard.
More information: Data Map Schema Reference
Specify the day offset in the range of -1 to 6, rather than 1 to 8.
Suggested Preparation in Your Source Files
To avoid import errors, verify that all date values are in the correct format before starting the Import Data Wizard.