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Evergreen date guide

What is celebrated on December 15?

See the observances and verified observance-history milestones attached to December 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.

2016
First observance

National Wear Your Pearls Day

National Day Calendar states that the inaugural year was December 2016, and the observance is fixed on December 15.

1999
Institutional decision

Vesak, the Day of the Full Moon

The United Nations Digital Library records adoption at the 79th plenary meeting on 15 December 1999.

1982
Institutional decision

Día de Andalucía

The decree is dated 15 December 1982 and records the Council of Government decision on that date.

1972
Institutional decision

World Environment Day

UN Digital Library records A/RES/2994 (XXVII) as adopted on 15 December 1972.

1941
First observance

Bill of Rights Day

The 1941 joint resolution and proclamation designated December 15, 1941 as Bill of Rights Day.

About this date

What this date contains

4 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.

2 have a country-specific scope

Country-specific observances are not presented as worldwide events.

4 have in-depth guides

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

Reviewed depth

Other in-depth guides on December 15

Source-backedFixed AnnualIn-depth guide

Bill of Rights Day

15 December · United States commemorative observance

Public Law 77-243, approved August 21, 1941, requested a presidential proclamation designating December 15, 1941 as Bill of Rights Day for the 150th anniversary of the Bill of Rights. Natio…

Source-backedFixed AnnualIn-depth guide

Cat Herders' Day

15 December · United States / creator-defined informal Wellcat observance

Thomas and Ruth Roy’s first-party Wellcat Holidays calendar lists Cat Herders' Day on 15 December and identifies the Wellcat holiday collection as their creation. The creator text frames th…

Source-backedFixed AnnualIn-depth guide

National Wear Your Pearls Day

15 December · United States / motivational observance founded by DeAnna Heard

National Day Calendar states that DeAnna Heard founded the observance, that its registrar approved it in 2015, and that it is observed on 15 December.

Explore the mix

Topics represented on December 15

All topics →
Arts, Entertainment & Lifestyle 2Civic, Remembrance & History 1Animals, Nature & Environment 1
4 observances

All observances on this date

Source-backedFixed AnnualIn-depth guide

Bill of Rights Day

15 December · United States commemorative observance

Public Law 77-243, approved August 21, 1941, requested a presidential proclamation designating December 15, 1941 as Bill of Rights Day for the 150th anniversary of the Bill of Rights. Natio…

Source-backedFixed AnnualIn-depth guide

Cat Herders' Day

15 December · United States / creator-defined informal Wellcat observance

Thomas and Ruth Roy’s first-party Wellcat Holidays calendar lists Cat Herders' Day on 15 December and identifies the Wellcat holiday collection as their creation. The creator text frames th…

Source-backedFixed AnnualIn-depth guide

National Wear Your Pearls Day

15 December · United States / motivational observance founded by DeAnna Heard

National Day Calendar states that DeAnna Heard founded the observance, that its registrar approved it in 2015, and that it is observed on 15 December.

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 →