<div dir="ltr">It looks like the <span style="font-size:12.8px">decree № 59 was not implemented and replaced by </span><span style="font-size:12.8px">decree № 147 <<a href="http://istmat.info/node/35854">http://istmat.info/node/35854</a>> which postponed the implementation until July 1, 1919. This is close to the date in tzdata, but it would still make more sense to have transition on a round UTC hour rather than at </span><span style="font-size:12.8px">21:28:41.</span></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Aug 23, 2016 at 11:57 PM, Alexander Belopolsky <span dir="ltr"><<a href="mailto:alexander.belopolsky@gmail.com" target="_blank">alexander.belopolsky@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><span class=""><br>On Tue, Aug 23, 2016 at 9:25 PM, Paul Eggert <<a href="mailto:eggert@cs.ucla.edu" target="_blank">eggert@cs.ucla.edu</a>> wrote:<br>>><br>>> What's the difference between MSM (Midsummer) and MDST (Moscow Double<br>>> Summer Time)? Both seem to be +05 = MSK + 2, but got different<br>>> abbreviations.<br>><br>><br>> The former differs from UT by an integer number of hours, the latter does not.<br><br></span>Interesting. It looks like the transition to integer offset from UTC is recorded as happening on Mon Jun 30 21:28:41 1919 UT (from zdump -v output.) However, according to this February 18, 1919 decree № 59 <<a href="http://istmat.info/node/35567" target="_blank">http://istmat.info/node/<wbr>35567</a>>, the GMT-based system of 11 zones (belts) went into effect on GMT midnight, April 1, 1919. The decree does not mention Moscow time, but the UTC+2 belt boundaries are defined by the state boundaries on the West and rivers Volga and Don on the east which places Moscow in UTC+2. The decree does not establish DST rules, but allows regional DST shifts by integer number of hours only.<br></div>
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