Here's a link to a CA family law website...
http://www.courtinfo.ca.gov/selfhelp/family/divorce/intro.htmLook around on the site. In part, it seems to say that you just need to file an ammendment to move an LSA to a D.
"If you file for a legal separation, you may later be able to file an amended petition to ask the court for a divorce..."
Also, you can get the advice from a "Family Law Facilitator" for free in CA (pretty nifty benefit!). Here's a link:
http://www.courtinfo.ca.gov/selfhelp/family/support/flf.htmThe instructions for the dissolution form have this note about the date of separation:
"Date of Separation (number 2b)
This is the date when you and your spouse knew your marriage was over, even if you were still living together. You may need to talk to a family law lawyer to decide what the “date of separation” was, especially if you and your spouse lived apart or had “trial separations” in the past.
ALERT! The date between the date of your marriage and date of separation will define the length of your marriage. The “Length of Marriage” can seriously affect the division of property and debts and payment of spousal support!"
So you may already have a date of separation on your original LSA paperwork.
The instructions for a judgement say to count 6 months plus one day from the date the other party is served, though. I'd check with the family law facilitator about what it all means.
I could be much more effective if it were my state, I know how to find al the laws and forms here. Hope this helps a little, anyway.