As I have been trying to understand a little bit more about Slavic pagan spirituality, one of the questions I had was whether there might be an analogous female deity to Kali within the Slavic pantheon. The consensus seems to be that this deity is Morena (in Slovakia, Marzanna in Poland, etc.). In fact, perhaps the most popular surviving pre-Christian ritual in Slovakia (and in some other Slavic countries) involves the ritual burning and immersion of Morena at the beginning of spring. She is generally taken to be a goddess of death and of winter. Her immolation and immersion is taken to be a ritual cleansing of the impurities that have accumulated during the winter months. At least in modern times, this is generally done at the time of the new moon following the vernal equinox. Thus, it is generally about 2 weeks prior to Easter. (Easter, of course, is the Sunday after the full moon following the vernal equinox.)
Here is a video about this ritual. (The video is in Slovak, but the general idea comes across anyway.) It counterpoints an adult ceremony with a ceremony in which a woman instructs children in the tradition.