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Evergreen date guide

What is celebrated on September 15?

See the observances and verified observance-history milestones attached to September 15. Each observance keeps its own source and date details.

Verified history

On this date in observance history

Today in history →

Selected observance milestones connected to this date, based on reviewed sources.

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…

2017
First observance

World Afro Day

World Afro Day first-party biography material states that the inaugural World Afro Day launched on 15 September 2017.

2016
First observance

National Online Learning Day

Learning Liftoff announced the upcoming first National Online Learning Day for September 15, 2016, and same-day institutional content confirms public observance.

2015
First observance

National Cheese Toast Day

Bake Magazine’s September 14, 2015 report says Sizzler would celebrate the day for the first time on September 15, 2015.

About this date

What this date contains

13 observances

Each observance is shown once in this view, with its own source and scope details available on the guide page.

0 repeat predictably

0 use a fixed annual date and 0 follow a reusable calendar rule.

0 are edition-specific

These dates are shown only for the year or edition that has been confirmed.

7 have a country-specific scope

Country-specific observances are not presented as worldwide events.

13 have in-depth guides

These pages include reviewed meaning, history, activities, facts and FAQs.

Reviewed depth

Other in-depth guides on September 15

Source-backedRule Based AnnualIn-depth guide

Get Ready Day

Third Tuesday in September; 15 September in 2026 · American Public Health Association / emergency preparedness

APHA holds Get Ready Day on the third Tuesday in September as part of its Get Ready preparedness campaign; APHA’s campaign archive describes a September 2007 event as the first-ever Get Rea…

Source-backedFixed AnnualIn-depth guide

Grito de Independencia / Grito de Dolores

15 September ceremony, preceding Mexico’s Independence Day on 16 September · Mexico; national independence commemoration tradition

Mexico’s Presidency verifies the September 15 national ceremony; Defense Ministry history places the historical Grito in the early hours of September 16, 1810, distinct from the September 1…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Costa Rica / mandatory paid national holiday

Costa Rica’s Labour Code and 2026 Ministry of Labour notice verify September 15 as a mandatory paid holiday, while Culture Ministry history links the annual date to the 15 September 1821 Ce…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · El Salvador / paid national independence holiday

El Salvador’s Labour Code lists September 15 as a paid day of rest, public-service law names it Independence Day, and Culture Ministry material ties the anniversary to the 15 September 1821…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Guatemala

Current Guatemalan government commemoration verifies the September 15 national anniversary and the 1821 independence-act identity; Decree 1618/current labour law independently verify later…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Honduras

Honduran judiciary history verifies the September 15, 1821 independence anchor in the Central American context; the Labour Code (Decree 189-59) separately includes September 15 among paid h…

Explore the mix

Topics represented on September 15

All topics →
Civic, Remembrance & History 6Community, Causes & Advocacy 4Workplace, Professions & Appreciation 1Food, Drink & Hospitality 1Health, Wellness & Awareness 1
13 observances

All observances on this date

Source-backedRule Based AnnualIn-depth guide

Get Ready Day

Third Tuesday in September; 15 September in 2026 · American Public Health Association / emergency preparedness

APHA holds Get Ready Day on the third Tuesday in September as part of its Get Ready preparedness campaign; APHA’s campaign archive describes a September 2007 event as the first-ever Get Rea…

Source-backedFixed AnnualIn-depth guide

Grito de Independencia / Grito de Dolores

15 September ceremony, preceding Mexico’s Independence Day on 16 September · Mexico; national independence commemoration tradition

Mexico’s Presidency verifies the September 15 national ceremony; Defense Ministry history places the historical Grito in the early hours of September 16, 1810, distinct from the September 1…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Costa Rica / mandatory paid national holiday

Costa Rica’s Labour Code and 2026 Ministry of Labour notice verify September 15 as a mandatory paid holiday, while Culture Ministry history links the annual date to the 15 September 1821 Ce…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · El Salvador / paid national independence holiday

El Salvador’s Labour Code lists September 15 as a paid day of rest, public-service law names it Independence Day, and Culture Ministry material ties the anniversary to the 15 September 1821…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Guatemala

Current Guatemalan government commemoration verifies the September 15 national anniversary and the 1821 independence-act identity; Decree 1618/current labour law independently verify later…

Source-backedFixed AnnualIn-depth guide

Independence Day

15 September · Honduras

Honduran judiciary history verifies the September 15, 1821 independence anchor in the Central American context; the Labour Code (Decree 189-59) separately includes September 15 among paid h…

Source-backedRule Based AnnualIn-depth guide

IT Professionals Day / IT Pro Day

Third Tuesday in September; 15 September 2026 · SolarWinds-created technology-professional appreciation observance

SolarWinds states that IT Pro Day began in 2015 and is observed on the third Tuesday of every September.

Source-backedFixed AnnualIn-depth guide

National Africa Civility Day

15 September · Africa-focused / World Civility Presidential Club-created humanitarian recognition observance

National Day Archives records September 15 and credits World Civility Presidential Club with founding the observance in 2020; current awareness calendars retain September 15.

Source-backedFixed AnnualIn-depth guide

National Cheese Toast Day

15 September · United States / Sizzler-created branded food observance

Sizzler’s own press releases celebrate National Cheese Toast Day on September 15 and identify the chain’s participation in the observance.

Source-backedFixed AnnualIn-depth guide

National Online Learning Day

15 September · United States / online-learning community observance registered in 2016

National Day Calendar states the observance was established in 2016 and proclaimed for September 15 annually; universities continue to recognize the same date.

Source-backedFixed AnnualIn-depth guide

National Tackle Kids Cancer Day

15 September · United States / Tackle Kids Cancer and Hackensack University Medical Center Foundation recognition

National Day Calendar identifies Hackensack University Medical Center Foundation as founder, places the observance on September 15 and records annual observance beginning in 2017. Current T…

Source-backedFixed AnnualIn-depth guide

World Afro Day

15 September · global Afro-hair celebration, education and anti-discrimination observance

World Afro Day organization; first event endorsed by the UN Office of the High Commissioner for Human Rights

How dates are selected

This page combines fixed annual dates, reusable calendar rules and year-specific dates confirmed for 2026. Variable or historical dates are included only when they are clearly supported.

Read the methodology →