Calcular intervalo de tempo no MySQL

SELECT 
    TRIM(REPLACE(CONCAT(
        IF(dy=0,'',IF(dy=1,'1 day ',CONCAT(dy,' days '))),
        IF(hr=0,'',IF(hr=1,'1 hr ', CONCAT(hr,' hrs  '))),
        IF(mn=0,'',IF(mn=1,'1 min ',CONCAT(mn,' mins '))),
        IF(sc=0,'',IF(sc=1,'1 sec ',CONCAT(sc,' secs ')))),'  ',' '))
    TimeDisplay
FROM (SELECT dy,hr,mn,MOD(sec_aaaa,60) sc
FROM (SELECT dy,hr,FLOOR((sec_aaa - dy*86400 - hr*3600)/60) mn,sec_aaa sec_aaaa
FROM (SELECT dy,FLOOR((sec_aa - (dy*86400))/3600) hr,sec_aa sec_aaa
FROM (SELECT FLOOR(sec_a/86400) dy,sec_a sec_aa
FROM (SELECT (UNIX_TIMESTAMP() - UNIX_TIMESTAMP('2011-02-01 00:00:00')) sec_a)
A) AA) AAA) AAAA) B;

DELIMITER $$

DROP FUNCTION IF EXISTS `test`.`GetTimeDisplay` $$
CREATE FUNCTION `test`.`GetTimeDisplay` (GivenTimestamp TIMESTAMP)
RETURNS VARCHAR(32)
DETERMINISTIC
BEGIN

    DECLARE rv VARCHAR(32);
    DECLARE diff BIGINT;

    SET diff = UNIX_TIMESTAMP() - UNIX_TIMESTAMP(GivenTimestamp);
    SELECT
        TRIM(REPLACE(CONCAT(
            IF(dy=0,'',IF(dy=1,'1 day ',CONCAT(dy,' days '))),
            IF(hr=0,'',IF(hr=1,'1 hr ', CONCAT(hr,' hrs  '))),
            IF(mn=0,'',IF(mn=1,'1 min ',CONCAT(mn,' mins '))),
            IF(sc=0,'',IF(sc=1,'1 sec ',CONCAT(sc,' secs ')))),'  ',' '))
    INTO rv
    FROM (SELECT dy,hr,mn,MOD(sec_aaaa,60) sc
    FROM (SELECT dy,hr,FLOOR((sec_aaa - dy*86400 - hr*3600)/60) mn,sec_aaa sec_aaaa
    FROM (SELECT dy,FLOOR((sec_aa - (dy*86400))/3600) hr,sec_aa sec_aaa
    FROM (SELECT FLOOR(sec_a/86400) dy,sec_a sec_aa
    FROM (SELECT ABS(UNIX_TIMESTAMP() - UNIX_TIMESTAMP(GivenTimestamp)) sec_a)
    A) AA) AAA) AAAA) B;

    IF diff = 0 THEN
        SET rv = '0 secs';
    END IF;
    IF diff < 0 THEN
        SET rv = CONCAT(rv,' From Now');
    END IF;
    IF diff > 0 THEN
        SET rv = CONCAT(rv,' Ago');
    END IF;

    RETURN rv;

END $$

DELIMITER ;

$query = "select country, rprice as regPrice, mprice as midPrice, pprice as prePrice, saddress as streetAddress,
                _id as ID, lat, lng, sname as Name, logo, admin_level_1 as state, locale as city, test.GetTimeDisplay(rdate) as regDate, 
                test.GetTimeDisplay(mdate) as midDate, test.GetTimeDisplay(pdate) as preDate, 
                format((acos(sin(radians($lat1)) * sin(radians(lat)) + cos(radians($lat1)) *
                cos(radians(lat)) * cos(radians($lng1) - radians(lng))) * 6378),1) as distance from stationDetails where 
                (acos(sin(radians($lat1)) * sin(radians(lat)) + cos(radians($lat1)) * cos(radians(lat)) * 
                cos(radians($lng1) - radians(lng))) * 6378) <= $rad order by $sort asc, $type asc";