Add n days to juliandate

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Asatur Khurshudyan
Asatur Khurshudyan on 23 Jan 2020
Hello everyone!
I am using
planetEphemeris(juliandate(y, m, d), 'Sun', 'Mars')
to extract the position of Mars relative to Sun at a given date
y, m, d.
Now, I need to add a specific number of days to that date and extract the position of the new date. Apparently,
planetEphemeris(juliandate(y, m, d) + n, 'Sun', 'Mars')
does not work. What do I need to add instead of n to have the position of Mars in, say, 100 days after that date?
Thank you in advance.

Accepted Answer

Robert U
Robert U on 23 Jan 2020
Hi Asatur Khurshdyan,
According to documentation example juliandate() you may use caldays() to add calendar days to a datetime-date.
planetEphemeris(juliandate(datetime(y,m,d)+caldays(n)), 'Sun', 'Mars')
Kind regards,
  1 Comment
Asatur Khurshudyan
Asatur Khurshudyan on 23 Jan 2020
Dear Robert,
Thank you for your answer. Sorry about missing that part from documentation.

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More Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 23 Jan 2020
It seems to work just fine as far as I can see. When I compare:
jd0 = juliandate(2020, 2, 14);
jd0p100 =juliandate(2020, 2, 14) + 100;
jd0p101 =juliandate(2020, 2, 14 + 100);
isequal(jd0p100,jd0p101) % returns true
jd0p101 - jd0 % returns 100
everything seems OK.
What is your problem? What matlab-version are you using?

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