May – List of International Days and Weeks

This information is from the United Nations website. The holiday date is below the holiday.
World Tuna Day (A/RES/71/124)

02 May
World Press Freedom Day (UNESCO 26 C/Resolution 4.3)

03 May
World Portuguese Language Day [UNESCO]

05 May
Time of Remembrance and Reconciliation for Those Who Lost Their Lives During the Second World War (A/RES/59/26)

08 May
International Day of Argania (A/RES/75/262)

10 May
World Migratory Bird Day [UNEP]

11 May
International Day of Plant Health [FAO] (A/RES/76/256)

12 May
International Day of Families (A/RES/47/237)

15 May
International Day of Living Together in Peace (A/RES/72/130)

16 May
International Day of Light [UNESCO] (39 C/Resolution 16)

16 May
World Telecommunication and Information Society Day (A/RES/60/252)

17 May
World Bee Day (A/RES/72/211)

20 May
International Tea Day (A/RES/74/241)

21 May
World Day for Cultural Diversity for Dialogue and Development (A/RES/57/249)

21 May
International Day for Biological Diversity (A/RES/55/201)

22 May
Vesak, the Day of the Full Moon (A/RES/54/115)

23 May
International Day to End Obstetric Fistula (A/RES/67/147)

23 May
Week of Solidarity with the Peoples of Non-Self-Governing Territories, 25-31 May (A/RES/54/91)

25 May
International Day of UN Peacekeepers (A/RES/57/129)

29 May
International Day of Potato (A/RES/78/123)

30 May
World No-Tobacco Day [WHO] (Resolution 42.19)

31 May
Source: un.org