diff --git a/Theory b/Theory index 4081b24..bd62c5c 100644 --- a/Theory +++ b/Theory @@ -240,12 +240,16 @@ locations differ in LMT. Historically, not only did different locations in the same zone typically use different LMT offsets, often different people in the same location maintained mean-time clocks that differed significantly, many people used solar or some other time -instead of mean time, and standard time often replaced LMT only gradually -at each location. As for leap seconds, we don't know the history -of earth's rotation accurately enough to map SI seconds to historical -solar time to more than about one-hour accuracy; see Stephenson FR -(2003), Historical eclipses and Earth's rotation, A&G 44: 2.22-2.27 -. +instead of mean time, and standard time often replaced LMT only +gradually at each location. As for leap seconds, civil time was not +based on atomic time before 1972, and we don't know the history of +earth's rotation accurately enough to map SI seconds to historical +solar time to more than about one-hour accuracy. See: Morrison LV, +Stephenson FR. Historical values of the Earth's clock error Delta T +and the calculation of eclipses. J Hist Astron. 2004;35:327-36 +; Historical +values of the Earth's clock error. J Hist Astron. 2005;36:339 +. As noted in the README file, the tz database is not authoritative (particularly not for pre-1970 time stamps), and it surely has errors.