date2seconds.m

function [secondsSinceYYYY] = date2seconds(date, startYear)
% % 
% % Calculate a date string of fixed formate to the number of seconds since 00 UTC
% % of 01 January of a given year. 
% % 
% % Input parameter(s):
% % date : date and time string of the formate YYYY-MM-DDTHH:MM:SS*;
% %        any characters at the end (*) are not used
% % startYear (optional) : year from which on seconds will be calculated
% % 
% % Output parameter(s):
% % secondsSinceYYYY : Number of seconds since input start year

if nargin < 2
   startYear = 1970;
end

nYears = str2num(date(1:4));
nMonths = str2num(date(6:7));
nDays = str2num(date(9:10));
nHours = str2num(date(12:13));
nMinutes = str2num(date(15:16));
nSeconds = str2num(date(18:19));

% convert number of years (excluding the current one) to number of days
yyyy = startYear;
numDays = 0;
while yyyy < nYears
    if (mod(yyyy,4)~=0)
        numDays = numDays + 365;
    else
        numDays = numDays + 366;
    end
    yyyy = yyyy + 1;
end

% convert number of months of current year to number of days
if (nMonths > 1)
    daysPerMonth = [31 28 31 30 31 30 31 31 30 31 30 31];
    mm = 1;
    while mm < nMonths
        numDays = numDays + daysPerMonth(mm);
        if ( mm==2 && mod(nYears,4)==0 )
            numDays = numDays + 1; 
        end
        mm = mm + 1;
    end
end

if (nDays > 1)
    numDays = numDays + (nDays-1);
end

secondsSinceYYYY = numDays*24*3600 + nHours*3600 + nMinutes*60 + nSeconds;