2024
First observance
National Pet Care for All Day
East Bay SPCA’s Winter 2024 publication calls April 24, 2024 the first National Pet Care for All Day celebration.
Evergreen date guide
What is celebrated on April 24?
See the observances and verified observance-history milestones attached to April 24. Each observance keeps its own source and date details.
Verified history
Today in history →On this date in observance history
Selected observance milestones connected to this date, based on reviewed sources.
2024
Institutional decision
National Pet Care for All Day
East Bay SPCA identifies April 24, 2024 as the establishment/launch date during its 150th anniversary.
2019
First observance
International Day of Multilateralism and Diplomacy for Peace
The United Nations Secretary-General’s 24 April 2019 message explicitly calls that date the first observance of the International Day of Multilateralism and Diplomacy for Peace.
1972
Institutional decision
Father’s Day — United States statutory observance
The Statutes at Large record gives 24 April 1972 as the approval date.
1972
Later action
Father’s Day — United States statutory observance
Permanently designated the third Sunday in June as Father’s Day and authorized/requested annual presidential proclamation.
Curated global anchors
See the collection →Major global guides on April 24
A reviewed starting point drawn from prominent global observances with strong institutional or organizer sources. Each observance keeps its own documented status and scope.
Source-backedFixed AnnualIn-depth guide
International Day of Multilateralism and Diplomacy for Peace
A/RES/73/127
Reviewed depth
Other in-depth guides on April 24
Source-backedRule Based AnnualIn-depth guide
Arbor Day
Arbor Day Foundation history verifies J. Sterling Morton’s January 4, 1872 proposal, the first Arbor Day on April 10, 1872, the 1874 Nebraska proclamation, the 1885 state-holiday stage and…
Source-backedFixed AnnualIn-depth guide
Día de Acción por la Tolerancia y el Respeto entre los Pueblos
Argentina Law 26.199
Source-backedRule Based AnnualIn-depth guide
National Hairball Awareness Day
The Animal Medical Center’s 2026 veterinary-awareness calendar and National Day Calendar both place Hairball Awareness Day on the last Friday in April.
Source-backedFixed AnnualIn-depth guide
National Pet Care for All Day
East Bay SPCA first-party records establish National Pet Care for All Day on April 24, 2024, identify that date as the first celebration, and tie it to the organization’s 150th anniversary…
Source-backedRule Based AnnualIn-depth guide
Undiagnosed Children’s Day
Genetic Alliance UK states that Undiagnosed Children’s Day is an annual SWAN UK awareness day on the last Friday in April and lists April 24 for 2026. SWAN UK is run by Genetic Alliance UK;…
Source-backedFixed AnnualIn-depth guide
World Day for Animals in Laboratories
The campaign’s official history identifies 24 April and traces the observance to 1979; NAVS also marks the date in current advocacy material.
Explore the mix
All topics →Topics represented on April 24
7 observances
All observances on this date
Source-backedRule Based AnnualIn-depth guide
Arbor Day
Arbor Day Foundation history verifies J. Sterling Morton’s January 4, 1872 proposal, the first Arbor Day on April 10, 1872, the 1874 Nebraska proclamation, the 1885 state-holiday stage and…
Source-backedFixed AnnualIn-depth guide
Día de Acción por la Tolerancia y el Respeto entre los Pueblos
Argentina Law 26.199
Source-backedFixed AnnualIn-depth guide
International Day of Multilateralism and Diplomacy for Peace
A/RES/73/127
Source-backedRule Based AnnualIn-depth guide
National Hairball Awareness Day
The Animal Medical Center’s 2026 veterinary-awareness calendar and National Day Calendar both place Hairball Awareness Day on the last Friday in April.
Source-backedFixed AnnualIn-depth guide
National Pet Care for All Day
East Bay SPCA first-party records establish National Pet Care for All Day on April 24, 2024, identify that date as the first celebration, and tie it to the organization’s 150th anniversary…
Source-backedRule Based AnnualIn-depth guide
Undiagnosed Children’s Day
Genetic Alliance UK states that Undiagnosed Children’s Day is an annual SWAN UK awareness day on the last Friday in April and lists April 24 for 2026. SWAN UK is run by Genetic Alliance UK;…
Source-backedFixed AnnualIn-depth guide
World Day for Animals in Laboratories
The campaign’s official history identifies 24 April and traces the observance to 1979; NAVS also marks the date in current advocacy material.
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 →