Talking about babusar pass.
in 2007 it opened in May.
in 2008 it opened in June
in 2009,it opened in July end (i think).
last year opened in July (2nd week).
It all depends upon the snowfall and weather conditions afterwards.
Less snow + more sunny days after words means it will open early and vise-versa.
Only a local can tell u exact position of pass.OR u'll come to know when u reach there.