calculating elapsed and remaining time between times.

 t1={'2011-10-01 11:12:00'};   \\ initial value of loop
    t2={'2012-03-31 23:09:00'};  \\ end value of loop
t11=datenum(t1(:));
t22=datenum(t2(:));
intrvl=datenum(0,0,0,0,1,0);    \\ loop interval in minutes.
ff=datenum(starttime(:));    \\ startime: <78678x1 cell> in {2016-12-06 5:51:10} format  
gg=datenum(stoptime(:));  \\ stoptime: <78678x1 cell> in {2016-12-06 5:51:10} format  
for t=t11:intrvl:t22;
    if(t > ff(loop-for-starttime) && t < gg(loop-for-stoptime))
body
    end
    end

My task is to check each value of loop ( starting from 2001-10-01 11:12:00 to 2012-03-31 23:09:00) if it is greater than starttime and less than stoptime and store searched values in a variable. if a condition is accepted it should calculate estimated time and remaining time for each searched values.

estimated time = etime(starttime,t)
remaining time= etime(stoptime,t)
kindly help.