RE:
"The COVID-19 pandemic has created a public emergency for purposes of rule 8.66 of the California Rules of Court. In light of the pandemic and the response thereto, it is ordered that, pursuant to rule 8.66(a)(2), the time to do any act required or permitted under the California Rules of Court is hereby extended by 30 additional days. No application for an extension shall be required. This order applies to Supreme Court proceedings in which the deadline for any action in the California Rules of Court occurs between March 20, 2020, through and including April 20, 2020. This order is effective immediately."
The Supreme Court has the power to extend deadlines set by the rules of court, but not deadlines set by statute. The deadline to appeal is set by the rules of court. The extension should apply to a petition for review. However, this is a new area and the order is not explicit. It would be safer to file based on the regular deadline.
My interpretation of the order would be that it applies to petitions for review. That said, if I had a deadline for a petition for review during this period, I would file the petition by that deadline, because the order is not crystal clear on that point. A case might not be considered a "Supreme Court proceeding" until the petition for review is actually filed and a case number assigned.