interval_value_exp

interval_value_exp 
      ::= 
      interval_term 
      | interval_value_exp_1 "+" interval_term_1 
      | interval_value_exp_1 "-" interval_term_1 
      | "(" datetime_value_exp "-" 
      datetime_term ")" interval_qualifier 

[rule list]
This rule is called by

-> datetime_value_exp -> extract_source -> interval_value_exp_1 -> set_time_zone_value -> time_zone_specifier -> value_exp