Smog Pump Julian Date Decode
 

Smog pump 7817872 with Julian Date 201781S. What day and year? Does this belong to a corvette?

Hi K,
Seems as though that casting number was used for a pump for various applications.
The date?.... 201st day of 1978?
?
Regards,
Alan

That pump could have been used on a Corvette but like Alan stated it was used on other applications. The judging manual reads the the 2nd, 3rd,& 4th were the Julian date and the 5th the year. There is no mention of what the 1st and 6th digits mean.

What date is on your trim tag?

Trim tag 3/78. So, the 201781, should read 017 day and year 78 per the 78-79 NCRS judging manual. I am looking for a period correct/julian date air pump for my 78 Pace. This one should work if read as 017 day and year 78. If, we read it as Alan states 201 day and year 78 this will not work.

Trim tag 3/78. So, the 201781, should read 017 day and year 78 per the 78-79 NCRS judging manual. I am looking for a period correct/julian date air pump for my 78 Pace. This one should work if read as 017 day and year 78. If, we read it as Alan states 201 day and year 78 this will not work.

. Alan, I have a 78 Pace, lookn for a period correct/julian date smog pump. If the info you gave me is correct, then this wont work. The 78-79 judging manual dictates the 1st and 6th digit are unknown. The 2nd, 3rd, and 4th are the julian date and the 5th is the year. So, it should read 017 day and 1978 as the year. Am I misinformed?

Oh and my trim tag is 3/78.

Hi K,
I'm sorry to put you off but I know VERY little about cars beyond the 72 model year.
Hopefully someone with 78 experience will be along.
Again, sorry I can't help.
Regards,
Alan

. Alan thank you for the assistance you gave me, dearly appreciated.

Not even close on the Julian date. Astronomers refer to a Julian date as the number of days since the beginning of the Julian Period (January 1, 4713 BC). You are trying to mix an ordinal date with a Julian date. Google how to determine the ordinal date of a Julian date.

Ignoring the terminal "S", which has no relevance in Julian dates, 201781 would be Sunday, B.C. 4161 Jun 12 - before Corvettes occurred. :)

Anyone, have more info on decoding this smog pump Julian date 201781. I am looking for the correct smog pump for my 78 Pace manufactured in 3/78. Is the Julian read as...017 day and 8 refers to 78. or as 201 day and 8 as 1978.

See my post directly above yours. It is not a "Julian" date.

See here: http://aa.usno.navy.mil/jdconverter?ID=AA&jd=201781

Read here. https://www.ncrs.org/forums/archive/...p/t-99179.html

Found this with a simple search on Google in less than 2 minutes.

It can be.
Emphasis added. Many parts have "Julian" dates.
:)

What you read in the Judging Guide and what Karol wrote is Correct.
Omit the first and sixth characters and you have the Julian date; 17th day of 1978.
Corvette pumps I've seen have the S on the end rather than other letters and the sixth character; 1 (I've been told) refers to the shift. What the first stands for ??? As Alan said, earlier pumps have only 5 numbers.
That pump has a very good date/match for your March car.
If you want another with a wrong date I'll send you a 108871S pump for 25. shipped Dated 88th day of 1977.

Source for your definition?

Admittedly, I went to an advanced university with emphasis on the sciences, so I am a purist when it comes to matters like this. But, these things do get bastardized over time. Read - dumbed down. But then, even Microsoft Excel adheres to the original definition.

Google. It gives your formal definition but also lists the more common example of a Julian date. "Dumbed down" is all we need for C3 part dates.
:)

Thank you for the clarification.

Duh. How about the link. Similar to how I gave on de-coding the date stamp. I have googled Julian date repeatedly and get the scientific definition everwhere.

Mathematicians and programmers have naturally interested themselves in mathematical and computational algorithms to convert between Julian day numbers and Gregorian dates. The following conversion algorithm is due to Henry F. Fliegel and Thomas C. Van Flandern:

The Julian day (jd) is computed from Gregorian day, month and year (d, m, y) as follows:

jd = ( 1461 * ( y + 4800 + ( m - 14 ) / 12 ) ) / 4 +
( 367 * ( m - 2 - 12 * ( ( m - 14 ) / 12 ) ) ) / 12 -
( 3 * ( ( y + 4900 + ( m - 14 ) / 12 ) / 100 ) ) / 4 +
d - 32075

Converting from the Julian day number to the Gregorian date is performed thus:

l = jd + 68569
n = ( 4 * l ) / 146097
l = l - ( 146097 * n + 3 ) / 4
i = ( 4000 * ( l + 1 ) ) / 1461001
l = l - ( 1461 * i ) / 4 + 31
j = ( 80 * l ) / 2447
d = l - ( 2447 * j ) / 80
l = j / 11
m = j + 2 - ( 12 * l )
y = 100 * ( n - 49 ) + i + l

Days are integer values in the range 1-31, months are integers in the range 1-12, and years are positive or negative integers. Division is to be understood as in integer arithmetic, with remainders discarded, and (m-14)/12 is -1 for m <= 2 and is 0 otherwise.

In these algorithms Julian day number 0 corresponds to -4713-11-24 GC, which is -4712-01-01 JC.

These algorithms are valid only in the Gregorian Calendar and the proleptic Gregorian Calendar. They do not correctly convert dates in the Julian Calendar.

It seems that the designers of these algorithms intended them to be used only with non-negative Julian day numbers (corresponding to Gregorian dates on and after -4713-11-24 GC). In fact they are valid (only) for dates from -4900-03-01 GC onward when converting from a Julian day number to a date, and (only) from -4800-03-01 GC onward when converting from a date to a Julian day number.

For other Gregorian/JDN conversion algorithms see Dr John Stockton's Gregorian Date to Day-Count and Day-Count to Gregorian Date.