If you have time data in the format other than YYYY-MM-DD HH:MM:SS & if you set timestamp as the datatype in HIVE Table, then hive will display NULL when queried.
You can use a simple trick here, Open your .csv data file in Microsoft Excel. Select the entire column, rightclick>Format Cells>Custom>type in the text box the required format (i.e. YYYY-MM-DD HH:MM:SS) and press OK/Apply. Your data will then be displayed in the Hive acceptable format of timestamp and will be loaded appropriately in HIVE. You can check it by querying HIVE.Cheers :)