The likely estimate of Kali yuga's duration is around 6000 years, as per René Guénon and Alain Daniélou, two authors that perfectly described what is going on now already a long time ago. They say there are many mistaken calculations out there about the yuga's duration. I think they are right since there was an important transition to farming, eating grains etc. around that time.This likely goes back to the beginning of this spiritual dark age - our yuga. That is likely many thousands of years.
Daniélou says the final, most extreme phase of Kali yuga began around 1940. Looking at the curves below I think this is indeed the case.
And obviously we must be right at the end of the yuga given the extremes we are facing now. Interesting times indeed!