See the posting from Lance Shipman at ESRI at http://forums.esri.com/Thread.asp?c=93&f=985&t=218476 where he says "Shapefiles only support date fields. Time is not supported."
Do you need to export to a shapefile, or are you able to use other spatial formats? A personal geodatabase won't exhibit the problem with the time field being reset.
I took these steps to create a single date/time field with your data:
- create a new personal geodatabase in ArcCatalog
- import your CSV table into this geodatabase as a table
- add a new field of type DATE
- add the table to ArcMap and open it
- right-click on the new field and calculate it to be:
[Date_] & " " & [Timestamp_]
You now have a table with X and Y coordinates, and the date/time in the same field, so you can convert this to an event layer and export to a featureclass. If you write the featureclass back into the same personal geodatabase, the time information will be preserved.
Otherwise, if you do need to use shapefiles, add a new Text field to the table and calculate it to be [Timestamp_]. This value will be preserved in the shapefile as a text string. The disadvantage of this is that you won't be able to perform analysis, like selecting events before or after a particular time.