public NumberExpression<Integer> dayOfMonth() {
        if (dayOfMonth == null) {
            dayOfMonth = Expressions.numberOperation(Integer.class, Ops.DateTimeOps.DAY_OF_MONTH, mixin);
        }
        return dayOfMonth;
    }
Create a day of month expression (range 1-31)

@return day of month
querydsl-core/src/main/java/com/querydsl/core/types/dsl/DateExpression.java