The definition of the second between 1956 and 1967 was 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12:00 ephemeris time, making this tropical year exactly 365.24219878125 days of 86,400 seconds. When I look into the Wikipedia article for tropical year to find out exactly what is meant by tropical year in this context, I find a table with two possibilities
shown at https://en.wikipedia.org/wiki/Tropical_year#18th_and_19th_century :
Leverrier's for which T is zero at January 0.5 and Newcomb's whose value at January 0.0 is the value I reckoned for days of 86,400 seconds rounded to the nearest millionth of a day. It is possible that Wikipedia has not got the exact details correct.
From: East Carolina University Calendar discussion List [mailto:[hidden email]] On Behalf Of Michael H Deckers
Sent: 01 September 2016 21:47
To: [hidden email] Subject: Re: Democratic Values Re: stand with me
On 2016-08-30 16:19, Bill Spencer wrote:
> France finished off the decimal Système
> international d’unités, (SI, metric).
> Time was added to SI only after electrical units
> were needed, in the late 19th and 20th centuries.
> But all those units were standardized around the
> old second = 1/86,400 day.
These are just a few of the many false claims in your post.
For an outline of the history of the metric system and the
SI you may for example consult the SI Brochure. There
you can find when the SI was established, and by whom,
and what the first definition of the SI second was.
You are in for a lot of surprises.