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There has been much debate about the exact beginning of the Third Millennium AD that has resulted from the astronomical use a year zero. I am grateful to the scholars quoted below for permission to quote from recent e-mail discussion touching on this subject, and to Fred Espanak of NASA permision to guote from his "Eclipse Predictions" wep page.

J.M.Steele. Thu May 23 10:01:24 1996

To: Ancient Near East list <>

"To further add confusion to the dating problem, it is the common use of historians of astronomy to use a system known as Julian Years to give a continuous dating system. In this system, there is a year 0 - it is the year before 1 AD. Hence year 0 = 1 BC, -1 = 2 BC, and so on. For comparing astronomical events in the past, such as the solar eclipse that was total in Babylon on 15 April 136 BC, it is much easier to call this year -135 April 15. For examples of dates of this kind, see the translation of the Babylonian astronomical diaries by Sachs and Hunger, or Sachs’ Late Babylonian Astronomical Texts (LBAT).

This may seem a strange system of dating to many Ancient Near East scholars, but believe me it is by far the best when dealing with ancient astronomy."

From t.sagrillo@utoronto.caThu May 23 10:02:24 1996

To: ANE List <>

"- astronomers START *counting* AT 0 (and thus the FIRST whole year is called "year 0", which would be *historical* year 1 CE), unlike historians who for some reason START at 1 (i.e., the "zero" point for historians is *not* 0, but 1 BCE/1 CE).

The 28 May 585 BCE date is the *historical* date of the eclipse; the astronomical date would be 28 May -584 (astronomers avoid the confusion of the BCE/CE label all together).

Just make sure, I confirmed this with my astronomy software (Voyager II 2.02). (I used Athens as a viewing point.) The results are:

Athens 23 deg. 43' E; 37 deg. 58' N

Processional epoch -583

Date: 28 May -584 (historical 585 BCE); Julian Date 1507900.089

Time: 16:08 (04:08 pm) local time, 14:08 Universal Time (GMT)

Altitude: +37 deg. 08'

Angle of separation between sun and moon: 20 deg. (i.e., not total)

Using Voyager II 2.02:


Date: 23 Oct. -527 (528 BCE); Julian Date 1528866.767

Time: 08:24 (08:24 am) local time, 06:24 Universal Time

Altitude: +18 deg. 40' (low to horizon)

Angle of sep.: 27 deg. (more than 28 May -584)

Also came up with:


Date: 30 June -530 (531 BCE); Julian Date 1527656.000

Time: 14:00 (2:00 pm) local time, 12:00 Universal Time

Altitude: +64 deg. 22'

Angle of sep.: 06 deg. (total eclipse)"

From J.M.Steele. Thu May 23 10:03:15 1996


"In order to calculate the circumstances of eclipses in the past, it is necessary to take full account of variations in the rotation of the Earth (for a discussion see Stephenson and Morrison, Phil. Trans. Royal Society of London, A, (1995) 351, 165-202). Many eclipse programs, and Oppolzer's canon, fail to do this."

From Thu May 23 10:03:21 1996

To: geoffrey summers <>

I ran the numbers in Voyager II for Ankara instead:

Date: 28 May -584 (historical 585 BCE); Julian Date 1507900.094

Time: 17:16 (05:16 pm) local time, 14:16 Universal Time (GMT)

Altitude: +28 deg. 30'

Angular separation between sun and moon: 14 deg. (not total but darker than Athens!)"

As John Steele notes, this programme is admittedly not 100% accurate. The manufacturer states that the programme uses resolutions of 1 min. of time and 1 min. of angle and is intended for a broad audiences -- including specifically archaeo-astronomers and scientists. While the *precise* numbers listed above are therefore somewhat suspect, it cannot be doubted that an eclipse did in fact occur on 28 May 585 BCE at about 5:15 pm and was visible in central Turkey."

From J.M.Steele. Thu May 23 10:04:26 1996

To: geoffrey summers < >

"There was an eclipse of the sun on 28 May 585 BC visible in the area you gave me. Here are the details assuming 35 deg east and 39 deg north :

Magnitude = 0.9627

UT at Max phase = 16.08 hours

Alt at Max phase = 6.4 degrees

This eclipse was not total, however given the uncertainties in position and Delta T (the clock error introduced by variations in the Earth's rate of rotation), it is possible that totality was observed somewhere in this area."

-0584 May 28   14:13   T   57   0.316   1.080    37.9N   42.4W   71   271   06m05s

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