public void setDay(String day) {
        this.day = day;
    }
This class represents the duration objects that needed to pass in to time conversion function for each database type
inorder to normalize the AGG_EVENT_TIMESTAMP
modules/siddhi-core/src/main/java/io/siddhi/core/aggregation/persistedaggregation/config/DBAggregationTimeConversionDurationMapping.java