"Millennial timescales" refers to a long period of time that spans over thousands of years, typically associated with the millennial generation. Full definition
In fact, it appears that the historical precedent for this earthquake occurred in July of the year A.D. 869 — dubbed the Jogan earthquake — based on paleo - tsunami findings as well as documents from that time, meaning that such large slips occur on millennial timescales whereas smaller quakes characterize the creeping subduction of roughly eight centimeters per year that occurs normally. (scientificamerican.com)
Superimposed on this trend are apparent dry — wet oscillations at centennial to millennial timescales most likely in response to solar activity.» (notrickszone.com)
Moreover, these driving forces were modulated in amplitude by signals with millennial timescales.» (watertechbyrie.com)