President Corazon Aquino and all the presidents after her are mandated to deliver the annual State of the Nation Address (SONA) in July.
The 1987 Philippine Constitution fixed the date of the SONA "every year on the fourth Monday of July." This is when the president "shall address the Congress at the opening of its regular session."
According to the Official Gazette's briefing piece on SONA traditions, the date of the SONA constantly changed before the 1987 Constitution:
The very first SONA was delivered by president Manuel L. Quezon on June 16, 1936, based on Commonwealth Act 17, which sets the opening of the sessions of the National Assembly on June 16 of every year.
The following year, the date was changed to October 16 via Commonwealth Act 49. But as the date fell on a Saturday, Quezon delivered the 2nd SONA on a Monday, October 18, 1937.
The date was moved to the 4th Monday of every year starting 1938 as mandated by Commonwealth Act 244.
However, Quezon delivered his last SONA on January 31, 1941, as he would already be in exile the following year because of the Japanese occupation.
1945-1946 – June
With the defeat of the Imperial Japanese Army in 1945, Congress convened on June 9. President Sergio Osmena delivered his SONA at provisional quarters in a converted school house at Lepanto Street in Manila.
President Manuel Roxas delivered the last SONA under the Commonwealth of the Philippines on June 3, 1946.
After the establishment of the independent Republic of the Philippines in 1946, the SONA was again set on the 4th Monday of January, based on Commonwealth Act 244, starting with Roxas’ address to the First Congress on January 27, 1947.
On January 23, 1950, President Elpidio Quirino, who was recuperating in a hospital at the US, delivered his SONA via radio broadcast picked up by the local radio network at 10 am.
The SONA was delivered on September 21 of each year to celebrate the anniversary of the imposition of martial law.
President Ferdinand Marcos delivered the 1978 SONA on June 12. From 1979 onwards, the SONA was delivered on the 4th Monday of July.
In 1983, the SONA was delivered on January 17 to commemorate the anniversary of the ratification of the 1973 Constitution and the second anniversary of the lifting of martial law.
No SONA was delivered from 1942 to 1944 because of World War II, and again in 1986. – Rappler.com