日期转换：年月日、年积日、简化儒略日、GPS周的MATLAB实现

function out_yd = wzq_ymd2yd(year,month,day)
%% convert year-month-day to days in year
% modified from: https://blog.csdn.net/qq_41696018/article/details/119647098
    doy = 0;
    days_in_month = [31,28,31,30,31,30,31,31,30,31,30,31];
    if(mod(year,4)==0 && (mod(year,100)~=0 || mod(year,400)==0))
        days_in_month(2)=29;
    end
    for i = 1:month-1
        doy = doy +days_in_month(i);
    end
    out_yd = doy+day;
end

function [year,month,day] = wzq_yd2ymd(year,doy)
%% convert days in year to year-month-day
% modified from: https://blog.csdn.net/qq_41696018/article/details/119647098
    days_in_month = [31,28,31,30,31,30,31,31,30,31,30,31];
    if(mod(year,4)==0 && (mod(year,100)~=0 || mod(year,400)==0))
        days_in_month(2)=29;
    end
    id = doy;
    month = 0;
    day   = 0;
    for i = 1:12
        id = id - days_in_month(i);
        month = i;
        if(id>0)
            continue
        end
        day = id + days_in_month(i);
        break
    end
end

function [year,month,day] = wzq_yd2ymd(year,doy)
%% convert days in year to year-month-day
% modified from: https://blog.csdn.net/qq_41696018/article/details/119647098
    days_in_month = [31,28,31,30,31,30,31,31,30,31,30,31];
    if(mod(year,4)==0 && (mod(year,100)~=0 || mod(year,400)==0))
        days_in_month(2)=29;
    end
    id = doy;
    month = 0;
    day   = 0;
    for i = 1:12
        id = id - days_in_month(i);
        month = i;
        if(id>0)
            continue
        end
        day = id + days_in_month(i);
        break
    end
end

function [year,doy] = wzq_mjd2yd(mjd)
%% ucas@Chistrong Wen
%  2022-10-17
    days   = [366,365,365,365];
    mjd52  = 34012;
    doy    = mjd+1-mjd52;
    i      = 1;
    year   = 52;
    while(doy>days(i))
        doy = doy-days(i);
        year = year+1;
        i = mod(year,4)+1;
    end
    if(year<1900)
        if(year>60)
            year = year +1900;
        else
            year = year +2000;
        end
    end
end

function [week,weekd] = mjd2gpsweek(mjd)
    week = (mjd-44244)/7;
    weekd = mjd-44244-week*7;
end

function mjd = gpsweek2mjd(week,weekd)
    mjd = week*7+44244+weekd;
end