As far as I know there is no such thing as winter time. Russia had standard time (UTC+3) in winter and changed to daylight savings time (UTC+4) at same dates as the rest of Europe. Now they decided never to switch back to UTC+3 but stay UTC+4, effectively making UTC+4 Moscow standard time.

As Moscows longitude is 37 degree East, they should really use UTC+3 as their standard time, but that's a different story.