The registration provisions of the Act are applicable to every person described in the Act, without regard to when his or her crime or crimes were committed or his or her duty to register pursuant to the Act arose, and to every offense described in the Act, regardless of when it was committed.
Source:
Section 290.023, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PEN§ionNum=290.023..