What does the lien date mean on my bill?

There is a lien for taxes on each property as of January 1st. This is a statutory lien, not a recorded lien. Per California Revenue & Taxation Code 2192: Lien Date "Except as otherwise specifically provided, all tax liens attach annually as of 12:01 a.m. on the first day of January proceeding the fiscal year for which the taxes are levied".