Glad to see you and thank you for your kind words!
In Russia, the whole year is divided into 4 seasons (as everywhere else))
Three months for each season. Spring is March, April and May. Therefore, March 1 is formally considered the beginning of spring.

In ancient times in Russia, the beginning of spring and even the new year was considered the day of the spring solstice on March 22-23. This is the real day of Maslenitsa among the Slavs. On this day, large round pancakes are baked as a symbol of the sun. And this date was permanent.

The Maslenitsa you wrote about is tied to the lunar calendar, it is a Christian Maslenitsa. This date, like the date of Easter, is not constant, it depends on the cycles of the moon.