If I want to search information within these seven days.
@timestamp:["now-7d" TO "now"]
If I want to search information between 2015-01-01 and 2015-01-31.
@timestamp:["2015-01-01" TO "2015-01-31"]
If I want to search information between 2015-02-01 13:00:00 and 2015-02-01 18:00:00.
@timestamp:["2015-02-01T13:00:00" TO "2015-02-01T18:00:00"]