@Ben That is amazing!
I have a small problem here:
Your rotation script works great in the editor, but when I load it onto my Sony Smartwatch 3 it is not…
Here is one of my watchfaces using your script, that I can see that problem on: Mellin - URWERK UR-106 Black Pink - watch face for Apple Watch, Samsung Gear S3, Huawei Watch, and more - Facer
For moon phase indicator try use this expression code:
((((((((((((((365*(#Dy#-1))+(((#Dy#-1)/4)-(((#Dy#-1)/4)%1)))-(((#Dy#-1)/100)-(((#Dy#-1)/100)%1)))+(((#Dy#-1)/400)-(((#Dy#-1)/400)%1)))+#DD#)+1)-735486)*24)*60)*60)+((((#DH#*3600)+(#Dm#*60))+#Ds#)-5880))-(3600*7))/5102886)*360)
hope this help =)
Thanks for answering me!
Unfortunately, it still gives me a different rotation in the editor and on my watch.
In the editor, the rotation is ok (but the rotation is rotated 90 degrees (in relation to those two images of dial moon phase you posted before)).
I compensated for that by rotating image I used as those 2 orbs.
BTW: what is that % symbol in this version of the script?
I cannot find it in documentation.
% is modulo a.k.a. the rest of the integer division, not sure on Facer, but in most language quite “glutton” in CPU.
Extremely useful to get the pari numbers:
0%2 = 0
1%2 = 1
2%2 = 0
3%2 = 1
…
(#DWFKS#*360) will be from 0 to 360 instead of 15 to 375 
Cheers,
P.
I kind of guessed that much.
What I’m asking: does that % actually work outside the editor, even tho it’s not in the “Math Expressions” part of the Facer Creator Documentation?
Whenever I need rest of the integer division in Facer I usually used something like this:
(((x/2)-floor(x/2))*2)
Using % would help me so much…
if it works.
Anyway, I created this:
((((((((((#DH#/24)+#DD#)*3)/1096)+#Dyyyy#)/(850481/10521600))-floor((((((((((#Dsm#/60)+#Dm#)/60)+#DH#)/24)+#DD#)*3)/1096)+#Dyyyy#)/(850481/10521600)))*180)+11)+90)
Based on moon’s phases period - (850481/10521600) in years.
It gives me back rotation of moon dial from 0-180 (where 90 is the full moon).
I still don’t know, why your script doesn’t work for me, but still, thank you for your help.
Hai Guys… i try to update calculation Moon Phase and would like to share mathematical formula for Moon Phase calculation for facer watchface following below:
JD = Julian Day SYNODIC_PERIOD = 29.530588853 // days for the mean synodic month JDNM = 2451550.1 // Julian Date A new moon occurred at (January 6, 2000). Then it is easy to count the number of days since the last new moon. JD = ((367*#Dy#-((7*(#Dy#+((#DM#+9)/12)))/4)+((275*#DM#)/9)+#Dd#+1721013.5+#Dk#/24)-0.5*((100*#Dy#+#DM#-190002.5)/abs(100*#Dy#+#DM#-190002.5))+0.5) A = (JD - JDNM) / SYNODIC_PERIOD B = (((A)-floor(A))*SYNODIC_PERIOD) Moon_Age = (Math.round((D*1000)/10)/100) // Round a Decimal value to 2 Decimal places xx.xx
Tag Expression Text:
Moon Age (Math.round((((((((367*#Dy#-((7*(#Dy#+((#DM#+9)/12)))/4)+((275*#DM#)/9)+#Dd#+1721013.5+#Dk#/24)-0.5*((100*#Dy#+#DM#-190002.5)/abs(100*#Dy#+#DM#-190002.5))+0.5)-2451550.1)/29.530588853)-floor((((367*#Dy#-((7*(#Dy#+((#DM#+9)/12)))/4)+((275*#DM#)/9)+#Dd#+1721013.5+#Dk#/24)-0.5*((100*#Dy#+#DM#-190002.5)/abs(100*#Dy#+#DM#-190002.5))+0.5)-2451550.1)/29.530588853))*29.530588853)*1000)/10)/100) Days
For Tag Expression Rotation:
((Math.round((((((((367*#Dy#-((7*(#Dy#+((#DM#+9)/12)))/4)+((275*#DM#)/9)+#Dd#+1721013.5+#Dk#/24)-0.5*((100*#Dy#+#DM#-190002.5)/abs(100*#Dy#+#DM#-190002.5))+0.5)-2451550.1)/29.530588853)-floor((((367*#Dy#-((7*(#Dy#+((#DM#+9)/12)))/4)+((275*#DM#)/9)+#Dd#+1721013.5+#Dk#/24)-0.5*((100*#Dy#+#DM#-190002.5)/abs(100*#Dy#+#DM#-190002.5))+0.5)-2451550.1)/29.530588853))*29.530588853)*1000)/10)/100)*12.19074911753505)
visit here for reference: G7 - SW Moonphase Indicator v1.6 - watch face for Apple Watch, Samsung Gear S3, Huawei Watch, and more - Facer
“Inspector Mode” Available 
I hope it will be useful for alls…
I know it’s a bit old thread, about calculating the Moon rotating, and Moon days. But Ben, despite you’r great Job with you’r calculation, it’s not correct. I took a look at you’r Link to the watch, which shows you’r rotating Moon, and the Lunar day, and the Moon goes much behind what’s correct. Take a look at my own Weather Site Aktuelle vejrdata fra Nakskov (look in the bottom of the Site)
It shows the exact position of the Moon, and where it is located on the Sky, and the Moon Rise, and Set.
I’m trying to figure out, an accurate script for Facer use, for the Moon rotation on a new watch I’m building up. Not a Moon rotating the traditionally way, but a fully rotation, showing images for each of the Moon days. But so far, it’s a bit of a “fight” to get it to works.
I tried doing it on Samsung’s Gear watch Designer, as they have a script build in to there designer, and it works perfectly on the minute; but unfortunately, you can’t see how this script are build 
Thank you for your comments…
All the moon phase that I post the calculations is just about any less
about fully rotation, showing images for each of the Moon days
maybe the links below can help.
about position of the Moon, and where it is located on the Sky, and the Moon Rise, and Set. it requires a very long script that is quite difficult to put on the line tag. if the facer can provide the use of lua script it may be helpful.
@G7 - Great Job! I noticed, that you have turned the “Moon Ring” 180 degrees wrong The Moon is waning now.
I look forwards to that day, where it will be implemented as Tag, to have the GPS info. Then it will be more Fun and interesting, to “play” with Sun and Moon positions, and the rotations.
yes… 
you right the moon is waning crescent now around 19 to 20 age days.
for the moment I have not seen providing about GPS info for implemented as Tag this link as a reference Tags | Facer Documentation
OH!!! i’ve been looking for modulo for so long! Hope Facer adds it to the docs
And BTW, I’ve been working on moonphase on my own and I’m not much of a mathematician, but it seems I’ve come up with something that works (U’ll find it here : https://www.facer.io/watchface/9L6tZ49qzs )
My Formula is much simpler (and therefore probably wrong) :
October 19 2017 (day 292) was a new moon so i get a second value for that day:
(292*86400)+(2017*31557600))
The Current day in second is:
((#DD#*86400)+(#Dy#*31557600))
I find the delta between the 2 values :
(((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))
Then I divise it by 29.5530588853 day (multiplied by seconds per day)
((((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))/(29.5530588853*86400))
Then i keep only the decimal
(((((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))/(29.5530588853*86400))-floor(((((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))/(29.5530588853*86400))))
Then I convert this into an angle starting from -90° and going to 90°:
(((((((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))/(29.5530588853*86400))-floor(((((#DD#*86400)+(#Dy#*31557600))-((292*86400)+(2017*31557600)))/(29.5530588853*86400))))*180)-90)
VOILA
Hi,
Love your moon phase. I would like to add one to my watch face as I fly a rescue helicopter with NVG’s and moon phases is incredibly important. Can you tell me where you got your moon image and any other instructions you could give me please?
Kind Regards,
Peter
Thanks. I found the image on google very simply. I used Moon Phases 2019 – Lunar Calendar to figure out the new moon date.
is this designed for use in both the northern and southern hemispheres?
Not really, It works fine in Paris France (where I live).
… But I suppose that if it works in Paris, you could adapt it to other places by checking Moon Phases 2019 – Lunar Calendar and changing my formula accordingly.
Basically what u need to change in my formula is the “292” (2 times). Find the Day-in-year number for a new moon day.
Oh and my formula works for a moon that starts its move at 9 o’clock and ends at 3 o’clock.
Sorry explaining this in english is not that easy
I’m switching on the inspector mode if u want to check it out. Good luck though, it’s a mess.
I’ve been looking over both calculations and can’t seem to get either to give super accurate results. Some phases appear to match up with various online moon calendars. However, other dates/phases appear to be off by 1-3 days. Does anyone have some additional ideas for this?
There has got to be an API or tag that can display this as an integer or percentage.
@ eradicator09 try this tag expression :
(floor(((((floor(365.25*((#Dy#-1)+4716))+(2-floor((#Dy#-1)/100)+floor(floor((#Dy#-1)/100)/4))-1096.5+#DD#+(#DH#/24+#Dm#/1440))-2451550.1)%29.530588853)/29.530588853)*100))%
hope this work
Thanks, that’s another way of looking at it. I thought I could add some accuracy to the original formula, but I discovered a small glitch. I wanted to use UTC for the current hour. Problem with UTC is there is no UTC equivalent for Dates. When I get to the mismatch between my current time zone and UTC, I’d see the moon date jump back and forth. Overall the original long version was fairly accurate.
The other primary issue is the moon orbits in an elliptic. If you’ve seen all the recent news about the Super Blue Blood Moon, then you can see that the moons phases are perfectly regular. 29.530588853 days is the mean of several hundred years of data. The actual can fluctuate from 29.18 to about 29.93 days (according to wiki). The best we can hope for is around 98-99% accuracy at any one point. Unfortunately this end up being mildly frustrating to me.
I did some additional internet searches and didn’t find any free APIs that offered any more than the 8 standard moon phases.
Anyway, here is the comparison of the 3 formulas in practice against 3/2/2018 which should be a full moon:
My formula is in the middle and not to far off from your original and new ones.
