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What is celebrated on August 17?

See the observances and verified observance-history milestones attached to August 17. Each observance keeps its own source and date details.

Verified history

On this date in observance history

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

About this date

What this date contains

7 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.

6 have a country-specific scope

Country-specific observances are not presented as worldwide events.

7 have in-depth guides

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

Reviewed depth

Other in-depth guides on August 17

Source-backedFixed AnnualIn-depth guide

Black Cat Appreciation Day

17 August · United States / animal-welfare and adoption-awareness observance

UPI reports that Wayne H. Morris started Black Cat Appreciation Day in 2011; ASPCA independently documents August 17 recurrence and continued shelter/adoption-awareness use.

Source-backedFixed AnnualIn-depth guide

Fête nationale / Independence anniversary of Gabon

17 August annually; 66th anniversary in 2026 · Gabon / national independence observance

The Presidency of Gabon documented the country’s national celebration on 17 August 2026 as the 66th anniversary of accession to international sovereignty.

Source-backedFixed AnnualIn-depth guide

Independence Day / Proclamation anniversary

17 August · Indonesia

Indonesia State Secretariat and official presidential holiday regulations verify the August 17 Proclamation anniversary, annual state ceremony and national-holiday framework.

Source-backedFixed AnnualIn-depth guide

National Massachusetts Day

17 August · United States / National Day Calendar National State Days series — Massachusetts

National Day Calendar lists National Massachusetts Day on 17 August. The U.S. Senate records Massachusetts’s admission/statehood date as 6 February 1788. The two dates are deliberately kept…

Source-backedFixed AnnualIn-depth guide

National Workers’ Comp Adjuster Day

17 August · United States / private professional-appreciation observance listed by National Day Archives

National Day Archives lists August 17 and attributes creation in July 2021 to Centre for Neuro Skills; the creator attribution is not treated as independently verified without a first-party…

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Topics represented on August 17

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Civic, Remembrance & History 5Workplace, Professions & Appreciation 2
7 observances

All observances on this date

Source-backedFixed AnnualIn-depth guide

Black Cat Appreciation Day

17 August · United States / animal-welfare and adoption-awareness observance

UPI reports that Wayne H. Morris started Black Cat Appreciation Day in 2011; ASPCA independently documents August 17 recurrence and continued shelter/adoption-awareness use.

Source-backedFixed AnnualIn-depth guide

Fête nationale / Independence anniversary of Gabon

17 August annually; 66th anniversary in 2026 · Gabon / national independence observance

The Presidency of Gabon documented the country’s national celebration on 17 August 2026 as the 66th anniversary of accession to international sovereignty.

Source-backedFixed AnnualIn-depth guide

Independence Day / Proclamation anniversary

17 August · Indonesia

Indonesia State Secretariat and official presidential holiday regulations verify the August 17 Proclamation anniversary, annual state ceremony and national-holiday framework.

Source-backedFixed AnnualIn-depth guide

National Massachusetts Day

17 August · United States / National Day Calendar National State Days series — Massachusetts

National Day Calendar lists National Massachusetts Day on 17 August. The U.S. Senate records Massachusetts’s admission/statehood date as 6 February 1788. The two dates are deliberately kept…

Source-backedFixed AnnualIn-depth guide

National Workers’ Comp Adjuster Day

17 August · United States / private professional-appreciation observance listed by National Day Archives

National Day Archives lists August 17 and attributes creation in July 2021 to Centre for Neuro Skills; the creator attribution is not treated as independently verified without a first-party…

Source-backedFixed AnnualIn-depth guide

Unification of Prekmurje Slovenes with the Mother Nation

17 August · Slovenia / national holiday that is not work-free

Slovenia’s current Holidays and Days Off Act lists August 17 as the incorporation of Prekmurje and unification of Prekmurje Slovenes with the mother nation and expressly keeps it non-work-f…

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.

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