If you were to look in the database or your import file you would see that most tables have Entered_by, Entry_date, Changed_by and Changed_date fields so when data in these tables are found to be duplicates of items already in the database, on the basis of the keys, they can all be compared on the basis of Entry_date and Changed_date to deternmine which is the latest. However, a few tables don’t have these fields, e.g. Location_sources, Name_sources, Sample_sources, Source and Taxon_occurrence_sources, so when users select All Latest to deal with duplicates in imports, Recorder 6 doesn’t know whether to reject the import or overwrite the item already in the database with the imported version, for these tables. If your import contains data in these tables you then get the message ‘Not all records could be compared on the basis of date stamps’. If you get this message you will need to decide whether to check these individually and select Accept Import or Reject Import or to use All Imported or All Original. If you examine the imported and original data, you may find that it is the same so selecting All Imported or All Original will have the same effect.