While it could be coincidence, I think you're onto something. If the attack was first discovered on Dec 10, that means Anthem notified the public on Day 59 (February 6 is the timestamp at the bottom of AnthemFacts.com). That is the last possible chance they have to legally notify the public.

The Wall Street Journal[1] notes that: "Federal law requires health-care companies to inform consumers and regulators when they suffer a data breach involving personally identifiable information, but they have as many as 60 days after the discovery of an attack to report it." Day 59 is cutting it awfully close.

[1] http://www.wsj.com/articles/health-insurer-anthem-hit-by-hac...