Russia permanently switched its clocks to summer time on Sunday in a change backed by President Dmitry Medvedev, who has said people and even cows suffer stress from getting up at a different time.
The move means that Moscow will be permanently four hours ahead of Greenwich Mean Time (GMT) but experts said people suffer no ill effects from changing clocks and questioned the need for the reform.
Medvedev announced in February that Russians would not put their clocks back this autumn, saying that the change from daylight saving time caused "stress and illness" and "disturbs the human biorhythm."
Somewhat bizarrely, he also voiced concern for farm animals, talking of "unhappy cows or other animals who don't understand the time change and don't understand that the milkmaid is going to milk them at a different time."
Experts said that research had not proved any ill effects to human health, however.
Research commissioned by the health ministry did not come up with any evidence to back the move, the acting director of Serbsky Institute psychiatric hospital, Zurab Kekelidze, told the Echo of Moscow radio station.
"The changes that were found were not reliable, that is they were not statistically significant. Therefore the change to winter time does not affect human health," the pyschiatrist said on Sunday.
"There has not been any proof that people suffer health problems," sleep disorders expert Sergei Yarosh told the RIA Novosti news agency.
A survey by the Levada independent polling agency published Friday found that a majority of Russians supported the reform, however, with 63 percent describing it as "positive."
The Soviet Union started switching to daylight saving time in 1981, with the aim of saving energy.
The country had already switched all its time zones one hour ahead under Stalin in 1930, meaning that Russia will now be permanently two hours ahead of its original time zones.
Medvedev has sought to leave his mark as president by making sweeping changes to the country's time zones.
Last year he abolished an entire time zone in central Russia and moved time back in the country's easterly-most region of Kamchatka, so that it is now eight instead of nine hours ahead of Moscow, prompting street protests.