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Evergreen date guide

What is celebrated on May 18?

For 2026, these source-backed observances resolve to Monday, May 18. Recurring rules can move in another year, so each record keeps its own date logic.

Date authority profile

What this date contains

10 unique authority records

The list is deduplicated at the public entity layer while retaining all research provenance behind each page.

0 stable or rule-calculated

0 fixed annual and 0 reusable rule-based records can be placed without inventing a new date.

0 edition-specific

Edition-specific dates appear only when the requested year matches the verified edition; variable and historical records remain gated.

7 explicit country-scope records

Country scope stays attached to the underlying record instead of being generalized into a worldwide observance.

0 reviewed in-depth guides

These entities add reviewed meaning, history, activities, facts and FAQs without rewriting the authority facts.

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Topics represented on May 18

All topics →
Civic, Remembrance & History 3Health, Wellness & Awareness 2Arts, Entertainment & Lifestyle 2Food, Drink & Hospitality 1Relationships & Family 1Workplace, Professions & Appreciation 1
10 date-resolved records

All observances on this date

Source-backedEdition Specific

Anniversary of the Battle of Las Piedras

18 May; 215th anniversary in 2026 · Uruguay / national historical commemoration

Uruguay’s Presidency documented the 215th anniversary commemoration of the Battle of Las Piedras on 18 May 2026 and described its place in the country’s independence-era history.

Source-backedFixed Annual

Constitution and State Flag Day

18 May each year · Turkmenistan

Turkmenistan government states the national observance is celebrated every year on 18 May

Source-backedFixed Annual

Fête du Drapeau et de l’Université

18 May annually; 2025 national ceremony verified · Haiti / national flag and university observance

The Government of Haiti documented official 18 May 2025 ceremonies for the Fête du Drapeau et de l’Université and described the date’s national symbolic importance.

Source-backedFixed Annual

HIV Vaccine Awareness Day

18 May annually · United States / NIH HIV research awareness

NIH states that HIV Vaccine Awareness Day is held annually on May 18 and recognizes volunteers, community members, health professionals and scientists working on preventive HIV-vaccine rese…

Source-backedFixed Annual

HIV Vaccine Awareness Day (HVAD)

18 May annually · United States / NIH HIV awareness observance

NIH HIVinfo states that HIV Vaccine Awareness Day is observed each year on May 18. The page title “World AIDS Vaccine Day” is treated as a search/legacy alias, not the authority’s official…

Source-backedFixed Annual

National Cheese Soufflé Day

18 May · Informal food-calendar usage documented by Association of Nutrition & Foodservice Professionals chapter material

Two Association of Nutrition & Foodservice Professionals chapter calendars list National Cheese Soufflé Day on 18 May.

Source-backedFixed Annual

National Visit Your Relatives Day

18 May · United States / informal family-connection observance

National Day Calendar and National Today independently place National Visit Your Relatives Day on May 18; Days Of The Year also lists it on May 18.

Source-backedFixed Annual

Send An Electronic Greeting Card Day

18 May · United States / creator-defined informal Wellcat observance

The first-party Wellcat calendar lists Send An Electronic Greeting Card Day on May 18.

Source-backedRule Based Annual

Supply Chain Professionals Day

Third Monday of May (18 May in 2026) · International supply-chain profession / CSCMP-created recognition day

CSCMP announced the inaugural annual Supply Chain Professionals Day in 2018, and trade coverage records the recurring rule as the third Monday in May.

How this date is built

This page is assembled from verified fixed dates, reusable recurrence rules, and target-year records whose edition matches 2026. Variable, historical or unresolved records are not silently forced onto this date.

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