An effectivity allows you to specify a time period during which a rule should be effective while engine execution. By assigning effectivity to a rule, you can control the period of rule execution.
While creating an effectivity, you can specify the following:
Date period
Days
Time
Discrete dates
Example
Rule A is effective every Wednesday , Saturday and Sunday from 2009-09-19T10:03:41 to 2009-09-30T10:03:44 but not on 2008-09-03
2009–09–28 is a discrete date.