I am a Canadian citizen and I have a question regarding my six year H1B limit. I started working on H1B from October 2006 until I was laid off in May 2008. Following my layoff, I changed my immigration status to H4. After being on H4 status for two months, I got a job using which I obtained a TN1 visa in July 2008. I remained on TN1 status until July 2009 at which time my company applied for and obtained H1B for me.

Timeline of Events:
H1B: Oct 2006-May 2008
H4: May 2008-July 2008
TN1: July 2008-July 2009
H1B: July 2009-Present

My H1B is currently set to expire in July 2012, and I was wondering if the time I spent on H4 and TN1 will be counted towards my six year H1B limit.

If I change to another company today, how much time can the new company claim for my H1B?

Thank you.