Moscow Time

Moscow Time (Russian: Моско́вское вре́мя) is the time zone for the city of Moscow, Russia, Belarus, and most of western Russia, including Saint Petersburg. It is the second-westernmost of the eleven time zones of Russia. It has been set to UTC+3 permanently on 26 October 2014; before that date it had been set to UTC+4 year-round since 27 March 2011.

Moscow Time is used to schedule trains, ships, etc. throughout Russia, while airplane travel is scheduled using local time. Times in Russia are often announced throughout the country on radio stations as Moscow Time, and this time is also registered in telegrams, etc. Descriptions of time zones in Russia are often based on Moscow Time rather than UTC. For example, Yakutsk (UTC+9) is said to be MSK+6 within Russia.

In accordance with the 16 June 1930 Decree of the Council of People's Commissars, the Decree Time was introduced by adding one hour to the time in each time zone of the USSR, so that Moscow Time became three hours ahead of Coordinated Universal Time.

Until 2011, during the winter, between the last Sunday of October and the last Sunday of March, Moscow Standard Time (MSK, МСК) was three hours ahead of UTC, or UTC+3; during the summer, Moscow Time shifted forward an additional hour ahead of Moscow Standard Time to become Moscow Summer Time (MSD), making it UTC+4.

In 2011, the Russian government proclaimed that daylight saving time would in future be observed all year round, thus effectively displacing standard time—an action which the government claimed emerged from health concerns attributed to the annual shift back-and-forth between standard time and daylight saving time. On 27 March 2011, Muscovites set their clocks forward for a final time, effectively observing MSD, or UTC+4, permanently.

...
Wikipedia