# When is the precise moment of tomorrow's solstice? **URL:** \ **Category:** Factual Questions\ **Created:** [June 20, 2013, 12:25pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455 "2013-06-20T12:25:28Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [June 20, 2013, 12:25pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/1 "2013-06-20T12:25:28Z")
Googling is failing me. I can find a lot of sites saying 05:04 UTC, but I’m looking for accuracy to the second. I’ve tried using [this](http://ssd.jpl.nasa.gov/horizons.cgi#results) page, but I must be doing it wrong, because I am getting a result of 09:43:32, which is obviously way off. ---
**Author:** ![Coriolanus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/coriolanus/32/18769_2.png) [@Coriolanus](https://boards.straightdope.com/u/Coriolanus)\ **Post date:** [June 20, 2013, 1:00pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/2 "2013-06-20T13:00:34Z")
This site: [Stellafane Equinox & Solstice Calculator](http://stellafane.org/misc/equinox.html) calculates the time as: Fri Jun 21 2013 01:03:36 GMT-0400 (Eastern Standard Time) I haven’t had any luck using NASA’s ephemerides generator [http://ssd.jpl.nasa.gov/horizons.cgi](http://ssd.jpl.nasa.gov/horizons.cgi) as it only goes down to minutes. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [June 20, 2013, 1:03pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/3 "2013-06-20T13:03:13Z")
> [@Ximenean](#): > > I’ve tried using [this](http://ssd.jpl.nasa.gov/horizons.cgi#results) page, but I must be doing it wrong, because I am getting a result of 09:43:32, which is obviously way off. Where does that page give the time of the solstice? ---
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [June 20, 2013, 1:08pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/4 "2013-06-20T13:08:06Z")
Thanks, **Coriolanus**. > [@Giles](#): > > Where does that page give the time of the solstice? I was trying to imitate the procedure on [this](http://answers.yahoo.com/question/index?qid=20110608221329AA7oGuG) page. I used the settings below and looked at the PAB-LON field, because it was the closest match to the longitude field that the guy on Yahoo Answers used. With trial and error I arrived at what seems to be a totally incorrect answer. Ephemeris Type [change] : OBSERVER Target Body [change] : Sun [Sol] [10] Observer Location [change] : Geocentric [500] Time Span [change] : Start=2013-06-21 09:40:32, Stop=2013-06-21 09:50:32, Step=1 m Table Settings [change] : defaults Display/Output [change] : default (formatted HTML) ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [June 20, 2013, 2:13pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/5 "2013-06-20T14:13:45Z")
It’s not noon? ---
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [June 20, 2013, 2:27pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/6 "2013-06-20T14:27:17Z")
Well it is if you’re somewhere like Cambodia. ---
**Author:** ![fiddlesticks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddlesticks/32/18129_2.png) [@fiddlesticks](https://boards.straightdope.com/u/fiddlesticks)\ **Post date:** [June 20, 2013, 3:43pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/7 "2013-06-20T15:43:41Z")
It’s a particular point of the Earth’s orbit, not Earth’s rotation. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 20, 2013, 3:58pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/8 "2013-06-20T15:58:29Z")
Can you really define the solstice to within a second, when you’re talking something as big as the earth? I suppose you can theoretically. Edit: I suppose the solstice is defined by the plane of the Earth’s tilted axis, which has zero width, right? ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [June 20, 2013, 4:11pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/9 "2013-06-20T16:11:58Z")
From: [Summer Solstice 2013 Friday](http://www.christianpost.com/news/summer-solstice-2013-friday-98418/) > [@](#): > > The 2013 summer solstice takes place on Friday, with people everywhere celebrating the longest day of the year. > It officially occurs when the sun is at the highest point possible in the sky on Friday at 1:04 a.m. EST and when the sun is directly over the Tropic of Cancer. ---
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [June 20, 2013, 4:14pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/10 "2013-06-20T16:14:38Z")
> [@Colophon](#): > > Can you really define the solstice to within a second, when you’re talking something as big as the earth? I suppose you can theoretically. > > Edit: I suppose the solstice is defined by the plane of the Earth’s tilted axis, which has zero width, right? No doubt there is some vagueness to it. Earth is not a perfect sphere, I imagine it wobbles slightly on its axis, etc. But these are very small imperfections. ---
**Author:** ![Munch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/munch/32/5281_2.png) [@Munch](https://boards.straightdope.com/u/Munch)\ **Post date:** [June 20, 2013, 5:24pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/11 "2013-06-20T17:24:45Z")
> [@bob\_2](#): > > From: [Summer Solstice 2013 Friday](http://www.christianpost.com/news/summer-solstice-2013-friday-98418/) > > > [@](#): > > > > The 2013 summer solstice takes place on Friday, with people everywhere celebrating the longest day of the year. > > It officially occurs when the sun is at the highest point possible in the sky on Friday at 1:04 a.m. EST and when the sun is directly over the Tropic of Cancer. :dubious: “Everywhere”? ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [June 20, 2013, 5:42pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/12 "2013-06-20T17:42:59Z")
Didn’t you hear? We’re shipping all the Australians, New Zealanders, (most) South Americans, and south Africans up to the Northern Hemisphere and throwing a massive kegger. ---
**Author:** ![newme](https://avatars.discourse-cdn.com/v4/letter/n/e0b2c6/32.png) [@newme](https://boards.straightdope.com/u/newme)\ **Post date:** [June 20, 2013, 8:43pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/13 "2013-06-20T20:43:21Z")
> [@Ximenean](#): > > Thanks, **Coriolanus**. > I was trying to imitate the procedure on [this](http://answers.yahoo.com/question/index?qid=20110608221329AA7oGuG) page. > > I used the settings below and looked at the PAB-LON field, because it was the closest match to the longitude field that the guy on Yahoo Answers used. With trial and error I arrived at what seems to be a totally incorrect answer. > > Ephemeris Type [change] : OBSERVER > Target Body [change] : Sun [Sol] [10] > Observer Location [change] : Geocentric [500] > Time Span [change] : Start=2013-06-21 09:40:32, Stop=2013-06-21 09:50:32, Step=1 m > Table Settings [change] : defaults > Display/Output [change] : default (formatted HTML) Instead of PAB-LON (Sun-Target-Observer angle), I believe you should use “Observer ecliptic lon. & lat.” [By definition](http://asa.usno.navy.mil/SecM/Glossary.html#_S), the Astronomical Summer Solstice (Northern Hemisphere) occurs at the moment the Sun’s ecliptic longitude is 90 degrees: > [@](#): > > solstice: > either of the two points on the [ecliptic](http://asa.usno.navy.mil/SecM/Glossary.html#ecliptic) at which the apparent longitude of the Sun is 90° or 270°; also the time at which the Sun is at either point. (See [longitude, ecliptic](http://asa.usno.navy.mil/SecM/Glossary.html#longitude-ecliptic).) I used the following settings and narrowed the solstice down to UTC 05:03:58.23 Ephemeris Type [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_type=1#top)] : \*\*OBSERVER \*\*Target Body [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_body=1#top)] : **Sun [Sol]** [10] Observer Location [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_loc=1#top)] : **Geocentric** [500] Time Span [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_time=1#top)] : Start= **2013-06-21 05:03:57.73** , Stop= **2013-06-21 05:03:58.73** , Intervals=\*\*2 \*\* Table Settings [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_tset=1#top)] : QUANTITIES= **31** ; time digits=\*\*FRACSEC \*\*Display/Output [[change](http://ssd.jpl.nasa.gov/horizons.cgi?s_disp=1#top)] : _default_ (formatted HTML) > [@](#): > > Date\_\_(UT)\_\_HR:MN:SC.fff ObsEcLon ObsEcLat > > * * * > > $$SOE > 2013-Jun-21 05:03:57.730 89.9999945 0.0000152 > 2013-Jun-21 05:03:58.230 90.0000000 0.0000152 > 2013-Jun-21 05:03:58.730 90.0000055 0.0000152 > $$EOE ---
**Author:** ![Ximenean](https://avatars.discourse-cdn.com/v4/letter/x/aca169/32.png) [@Ximenean](https://boards.straightdope.com/u/Ximenean)\ **Post date:** [June 20, 2013, 10:15pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/14 "2013-06-20T22:15:49Z")
Ah, I didn’t look at the Table Settings section. I wonder who’s right, you or **Coriolanus** ’s page? Wouldn’t want to be one of those druids at Stonehenge sacrificing a goat twenty seconds too early. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [June 21, 2013, 11:16pm UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/15 "2013-06-21T23:16:46Z")
> [@fiddlesticks](#): > > It’s a particular point of the Earth’s orbit, not Earth’s rotation. This confuses me, since they always say it’s when the sun is highest overhead. Well, obviously, it’s not going to be the highest overhead everywhere in the world at the same time, so I always thought the solstice was also rotation based (as scientists can define terms however they want). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 22, 2013, 12:16am UTC](https://boards.straightdope.com/t/when-is-the-precise-moment-of-tomorrows-solstice/661455/16 "2013-06-22T00:16:10Z")
The “when the Sun is highest overhead” definition is clearly flawed, since equatorial regions will have two dates when that happens, one each before and after the solstice. A better definition would be that it’s when the Sun is at maximum declension, and that doesn’t depend on where on the Earth you are.