I've notice some slight inconsistencies in the way numbers are handled with custom slots. "nineteen eight nine" => 1,989 "two thousand and one" => 2001 "two thousand and ten" => 2010 It's not just that these aren't handled in a consistent way. But the natural explanation - that some are interpreted as dates and others and numbers - actually works against expectations. It seems that the first example should be handled as a date, and the last as a number. (The second example is tricky, since that number/date is also a well-known name.) I still tend to stick with AMAZON.LITERAL slots instead of the much less tedious CUSTOM slots because I often find the results they return more consistent.