<p>The answer depends on what you mean with "precisely".  The <a href="http://adsabs.harvard.edu/abs/1983A&amp;A...124...50C" rel="nofollow">ELP theory</a> seems to have an accuracy of ~10<sup>-6</sup>&deg; in longitude over a century, which comes down to about a millisecond for phases.</p>

CC BY-SA 4.0
2022-02-12T21:32:33.850Z
Note, they used JPL DE200 and their program's own internal precision as an accuracy comparison, not actual observations.  DE200 is a numerical simulation.  Historical accuracy cannot be verified, but is assumed to be very precise.  In their paper, they show a disagreement with DE200 of -.00111 arcseconds over one century.  The paper also contains a lot more about accuracy for those interested.
https://articles.adsabs.harvard.edu/full/1983A%26A...124...50C
Greg Miller
CC BY-SA 3.0
2016-07-08T16:37:08.353Z
2016-07-08T16:37:08.353Z
AstroFloyd
<p>Moon circles around the earth in 29.5 day , if you multiply that by 24 hours then by 60 minutes and then by 60 seconds you get number of seconds in between moon cycles, this number never changes it is always the same</p>

CC BY-SA 4.0
2022-02-12T01:14:15.120Z
The interval from New Moon to New Moon is not constant. It varies by approximately 6 hours.
JohnHoltz
CC BY-SA 4.0
2022-02-11T23:02:23.483Z
2022-02-11T23:02:23.483Z
Jack
<p>The motion of the moon is known with great accuracy, and so the exact moment of a new moon (the moment that the sun and moon have the same longitude in the sky) can be calculated with great accuracy for tens of thousands of years into the future. This is the astronomical meaning of New moon, and the only one which is relevant here. The uncertainty is due to effects such as the non-spherical nature of the Earth's gravity and the exact magnitude of perturbations of the orbit by other bodies.</p>

<p>Unless there is an eclipse, the moon is not visible at the moment of the new moon, and doesn't become visible until some time later (<a href="https://astronomy.stackexchange.com/questions/14265/how-soon-could-a-waxing-crescent-moon-be-seen?rq=1">How Soon Could a Waxing Crescent Moon Be Seen?</a>). The time when the moon can be seen for the first time depends on lots of factors, such as atmospheric clarity, weather and latitude, these can't be predicted from day to day.</p>

CC BY-SA 4.0
2021-04-13T14:07:43.413Z
if you graph them, the wave pattern is interesting https://drive.google.com/file/d/1jTKPhukdYqVblev8RsBDnllhi0qprgIf/view
Andrew Arrow
CC BY-SA 4.0
2021-04-13T14:13:08.027Z
this data is from https://gist.github.com/andrewarrow/b6c39c8898e6ae7c1d3fed6f35b150c7
Andrew Arrow
CC BY-SA 3.0
2016-07-08T23:08:45.590Z
2017-02-22T13:46:18.903Z
2017-04-13T12:59:06.910Z
James K
<p>I wonder, how accurate the lunar calendar is?
Can we predict the new moons precisely for tens of years in future?
If we know all factors that affects the movement of the moon, then why it is not possible to predict it?</p>

CC BY-SA 3.0
2016-07-06T12:14:12.787Z
Great question!  I'd love to know this.
Fattie
CC BY-SA 3.0
2016-07-08T21:57:47.250Z
This depends on the definition of a new moon: conjunction with the sun, or the first visible crescent after that?
Mike G
CC BY-SA 3.0
2017-02-22T08:08:08.607Z
I can give the accurate lunar calendar for next 100 years But I need a guide and some support
WASIQ Shan
<moon-phases><the-moon>
lunar calendar accuracy for predicting new moons
M.M
# lunar calendar accuracy for predicting new moons

(Asked by: username_0 on 2016-07-05)

I wonder, how accurate the lunar calendar is?
Can we predict the new moons precisely for tens of years in future?
If we know all factors that affects the movement of the moon, then why it is not possible to predict it?

**Tags:** moon-phases, the-moon

> **Comments:**
> **username_1**: Great question!  I'd love to know this.  
> **username_2**: This depends on the definition of a new moon: conjunction with the sun, or the first visible crescent after that?  
> **username_3**: I can give the accurate lunar calendar for next 100 years But I need a guide and some support  

---

## 3 answers

### Answer by username_8 on 2016-07-08. Score: 4 | Accepted answer

The motion of the moon is known with great accuracy, and so the exact moment of a new moon (the moment that the sun and moon have the same longitude in the sky) can be calculated with great accuracy for tens of thousands of years into the future. This is the astronomical meaning of New moon, and the only one which is relevant here. The uncertainty is due to effects such as the non-spherical nature of the Earth's gravity and the exact magnitude of perturbations of the orbit by other bodies.

Unless there is an eclipse, the moon is not visible at the moment of the new moon, and doesn't become visible until some time later ([How Soon Could a Waxing Crescent Moon Be Seen?](https://astronomy.stackexchange.com/questions/14265/how-soon-could-a-waxing-crescent-moon-be-seen?rq=1)). The time when the moon can be seen for the first time depends on lots of factors, such as atmospheric clarity, weather and latitude, these can't be predicted from day to day.

> **Comments:**
> **username_9**: if you graph them, the wave pattern is interesting https://drive.google.com/file/d/1jTKPhukdYqVblev8RsBDnllhi0qprgIf/view  
> **username_9**: this data is from https://gist.github.com/andrewarrow/b6c39c8898e6ae7c1d3fed6f35b150c7  

---

### Answer by username_4 on 2016-07-08. Score: 3

The answer depends on what you mean with "precisely". The [ELP theory](http://adsabs.harvard.edu/abs/1983A&A...124...50C) seems to have an accuracy of ~10-6° in longitude over a century, which comes down to about a millisecond for phases.

> **Comments:**
> **username_5**: Note, they used JPL DE200 and their program's own internal precision as an accuracy comparison, not actual observations.  DE200 is a numerical simulation.  Historical accuracy cannot be verified, but is assumed to be very precise.  In their paper, they show a disagreement with DE200 of -.00111 arcseconds over one century.  The paper also contains a lot more about accuracy for those interested. https://articles.adsabs.harvard.edu/full/1983A%26A...124...50C  

---

### Answer by username_6 on 2022-02-11. Score: -4

Moon circles around the earth in 29.5 day , if you multiply that by 24 hours then by 60 minutes and then by 60 seconds you get number of seconds in between moon cycles, this number never changes it is always the same

> **Comments:**
> **username_7**: The interval from New Moon to New Moon is not constant. It varies by approximately 6 hours.  

---

