Under RA 388 last line, you will see there that the New Civil Code was approved on June 18, 1949. However, it specifically provided that it shall take effect one year after its publication.

The major consensus is that the New Civil Code took effect on August 30, 1950. This would also mean, that from the time of approval by Congress on June 18, 1949, it took them until August 30, 1949 to publish the New Civil Code in the Official Gazette or newspaper of general circulation.