2018
Precursor
World Cleanup Day
The global movement was already running same-name World Cleanup Day editions when the United Nations General Assembly proclaimed an annual UN World Cleanup Day on 20 September in…
Verified observance history
On this day: September 15
Exact-date milestones already verified in the authority base: first observances, institutional decisions, later actions and documented precursors.
Date distance
How far away is September 15?
Fast calendar-day answers, without creating separate thin pages for every query.
How long until September 15?TodayNext: September 15, 2026
How long ago was September 15?TodayPrevious: September 15, 2026
Verified history
Today in history →Verified milestones on September 15
These are exact-date milestones already verified in this observance authority base—not a general unsourced history feed.
What this page includes
This is intentionally narrower than a general history encyclopedia. It only surfaces exact dates already verified while researching observances, so month-only or ambiguous historical claims stay out.
Read the methodology →