Question about the Spring Equinox

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Kernix
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Question about the Spring Equinox

Post by Kernix »

So I saw a video on Youtube titled Astrology Day and it was posted on March 21st. I thought it was interesting to pick that day for a so-called Astrology day, but it made sense. That made me look at a calendar that I make every month which I have sunrise & sunset times so that I can calculate planetary hours for any one day. When I looked at the times for March 21st last month, I noticed that there was an 11 minute difference, but there was less than a minute difference for March 17th. Shouldn't the day where the length of night equals the length of day occur on the 21st? Am I missing something? I'm using calendars with sunrise\set times for Philadelphia PA USA which is almost 40 deg N. Lat and just over 75 deg W. Long. Can't see how the latitude or longitude would make a difference but thought I'd mention it. Here are some links I found that show the sunrise & sunset times for Philadelphia for March:

https://www.timeanddate.com/sun/usa/phi ... &year=2018

This one shows sunrise \ sunset as 7:08 & 7:09 (Daylight savings time, it should be 6:08 AM & 6:09 PM), daylight length for 3/17 is 12:00:40 so 40 secs diff between night and day but for the 21st it’s 12:11:16, over 11 mins difference.

https://www.sunrisesunset.com/calendar. ... e=0&wsom=0

This one has sunrise \ sunset for the 17th as 7:10 AM & 7:09 PM – slightly different times but still a min difference. How can it be that the equinox ("Equal Night") be 4 days earlier that what we consider the equinox? Does this happen every year?
Kernix
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Re: Question about the Spring Equinox

Post by admin »

Hi Kernix,

It's latitude that changes this 'equal night and day' matter.

This link explains it well: https://www.timeanddate.com/astronomy/e ... equal.html

Admin.
"Don't let the illusions of your past or future rob you of the infiniteness of your present." [Unknown]
Kernix
Posts: 11
Joined: Fri Jan 05, 2018 11:15 pm
Location: Philadelphia, PA USA
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Re: Question about the Spring Equinox

Post by Kernix »

Wow, that's messed up - thought the dates were selected when the celestial equater intersects with the ecliptic. Looks like they may be taking an average of the southern & northern hemisphere dates at the mid-point of 45 degrees - for both equinoxes. Thanks for the link.
Kernix
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Re: Question about the Spring Equinox

Post by admin »

Well, you've got me thinking more on this now ! Hmmm.

Admin.
"Don't let the illusions of your past or future rob you of the infiniteness of your present." [Unknown]
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