how to write a function that calulates the days until next birthday from now in matlab

main.m
function days_until_birthday = calc_days_until_birthday(year, month, day)
% This function takes a person's birthday in year-month-day format and
% calculates the number of days until their next birthday from the current
% date.
%
% Example usage:
% >> today = datetime('now');
% >> days_until_birthday = calc_days_until_birthday(1990, 3, 12)
% 
% days_until_birthday =
%
%     276
%
% >> next_birthday = today + days_until_birthday;
% >> disp(['Your next birthday is on ' datestr(next_birthday, 'dddd, mmmm dd, yyyy')])

this_year_birthday = datetime(year, month, day);
this_year_birthday.Year = year;
next_birthday = this_year_birthday;
if next_birthday < datetime('now')
    next_birthday.Year = next_birthday.Year + 1;
end
days_until_birthday = days(next_birthday - datetime('now'));
end
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main.m
>> today = datetime('now')
today =
   14-Dec-2021 11:16:53
>> calc_days_until_birthday(1990, 3, 12)
ans =
   77
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