public static <D extends Comparable> NumberExpression<Integer> datediff(DatePart unit,
            DateTimeExpression<D> start, DateTimeExpression<D> end) {
        return Expressions.numberOperation(Integer.class, DATE_DIFF_OPS.get(unit), start, end);
    }
Get a datediff(unit, start, end) expression

@param unit date part
@param start start
@param end end
@return difference in units
querydsl-sql/src/main/java/com/querydsl/sql/SQLExpressions.java