word | | Constitution |
| March | Puerto Rico | ratified 3 March 1952; approved by US Congress 3 July 1952; effective 25 July 1952 |
| March | Sao Tome and Principe | approved March 1990, effective 10 September 1990 |
| March | Syria | 13 March 1973 |
| March | Timor-Leste | 22 March 2002 (based on the Portuguese model) |
| March | United States | 17 September 1787, effective 4 March 1789 |
| Mariana | Northern Mariana Islands | Constitution of the Commonwealth of the Northern Mariana Islands effective 1 January 1978; Covenant Agreement fully effective 4 November 1986 |
| May | Argentina | 1 May 1853; amended many times starting in 1860 |
| May | Austria | 1920; revised 1929; reinstated 1 May 1945; note - during the period 1 May 1934-1 May 1945 there was a fascist (corporative) constitution in place |
| May | Burma | 30 May 2008 |
| May | Cameroon | 20 May 1972 approved by referendum, adopted 2 June 1972; revised January 1996 |
| May | Cyprus | ... the Turkish Cypriots declared their independence in 1983; a new constitution for the "TRNC" passed by referendum on 5 May 1985, although the "TRNC" remains unrecognized by any country other than Turkey |
| May | Egypt | 11 September 1971; amended 22 May 1980, 25 May 2005, and 26 March 2007 |
| May | Eritrea | a transitional constitution, decreed on 19 May 1993, was replaced by a new constitution adopted on 23 May 1997, but not yet implemented |
| May | European Union | ... was scheduled to take effect on 1 November 2006; defeat in French and Dutch referenda in May-June 2005 dealt a severe setback to the ratification process; in June 2007, the European ... |
| May | Germany | 23 May 1949, known as Basic Law; became constitution of the united Germany 3 October 1990 |
| May | Guatemala | 31 May 1985, effective 14 January 1986; note - suspended 25 May 1993 by former President Jorge SERRANO; reinstated 5 June 1993 following ouster of president; amended November 1993 |
| May | Guinea-Bissau | 16 May 1984; amended 4 May 1991, 4 December 1991, 26 February 1993, 9 June 1993, and in 1996 |
| May | Haiti | ... military government claimed to be observing the constitution; returned to constitutional rule in October 1994; constitution, while technically in force between 2004-2006, was not enforced; returned to constitutional rule in May 2006 |
| May | Israel | ... Establishment (1948), the Basic Laws of the parliament (Knesset), and the Israeli citizenship law; note - since May 2003 the Constitution, Law, and Justice Committee of the Knesset has been working on a ... |
| May | Japan | 3 May 1947 |
| May | Kyrgyzstan | adopted 5 May 1993; note - amendment proposed by President Askar AKAYEV and passed in a national referendum on 2 February 2003 significantly expanded the powers of the president at the expense of ... |
| May | Lebanon | 23 May 1926; amended a number of times, most recently Charter of Lebanese National Reconciliation (Ta'if Accord) of October 1989 |
| May | Malawi | 18 May 1994 |
| May | Marshall Islands | 1 May 1979 |
| May | Micronesia, Federated States of | 10 May 1979 |
| May | Nauru | 29 January 1968; amended 17 May 1968 (Constitution Day) |
| May | Nigeria | new constitution adopted 5 May 1999; effective 29 May 1999 |
| May | Norway | 17 May 1814; amended many times |
| May | Poland | adopted by the National Assembly 2 April 1997; passed by national referendum 25 May 1997; effective 17 October 1997 |