A proposal becomes a rule.

LitecoinPool.org’s April 28, 2017 notice recorded SegWit lock-in at the end of an activation period and identified the later activation boundary. Litecoin Core now records SegWit activation height 1,201,536. The public block record dates that height to May 10, 2017. These are separate milestones in a coordinated software change.

A signal is evidence of readiness or support in the specified mechanism. Lock-in establishes that the relevant threshold has been reached. Activation is when the new rules become effective under that deployment. Compressing the three into a single announcement conceals useful information about how a public network changes.

The educational value goes beyond the acronym. Readers can ask the same sequence of questions about later upgrades: Which software contains the change? What triggers it? Has that trigger actually occurred? What must applications do afterward? Litecoin’s SegWit episode belongs in the anniversary because it supplies a concrete example of technical coordination becoming a permanent part of a chain’s history.