Hi,

You need to ensure following format of search query e.g.:
EventDate:[200902020101 TO 200906020101]
It means you need to define interval with (hours and minutes) as well as the name of the field, that contains date value.

Please find more information about this approach at following link:

http://devnet.kentico.com/docs/devguide/index.html?smart_search_search_syntax.htm

Smart search is based on lucene.net so additionally, please take a look at lucene.net query syntax

http://lucene.apache.org/java/2_4_0/queryparsersyntax.html


Best regards,
Michal Legen