The president wrote on Facebook, Censor.NET reports.
"Sept. 1, 2017 is the day that will make it into history of our strong and independent Ukraine. Today, the Association Agreement between Ukraine and EU is coming into full effect," Poroshenko wrote.
The president reminded that the free trade area between Ukraine and the EU has been in place since Jan. 1, 2016.
"Over six months of this year, foreign goods and services trade between Ukraine and the EU countries has increased by 22 percent. Almost 40 percent of our trade is done with the European Union."
Poroshenko also said that a historical change of the geographical structure of the Ukrainian export has occurred, and the volumes of EU exports increased: "These are irreversible processes of integration of the Ukrainian economy in the EU market."
Many parts of the Association Agreement have been provisionally applied since 2014, but the adoption of the agreement will ensure closer cooperation between the EU and Ukraine in areas such as foreign policy, justice, education, science and technology.
The economic part of the agreement, called the Deep and Comprehensive Free Trade Area (DCFTA), is also intended to open up the EU market to Ukrainian goods and will align the Ukrainian economy with EU standards by harmonizing laws and regulations
Russia has indicated that it objects to the EU-Ukraine trade pact. Minutes of the June 29 meeting of the World Trade Association's Committee on Regional Trade Agreements that were published on July 11 record Russia's representative as saying the EU-Ukraine DCFTA was "an exemplary case of a situation where a free trade area worsened trade conditions for other trading partners."
Current Ukrainian President Petro Poroshenko signed the EU agreement in June 2014, but it remained unratified after 61 percent of Dutch voters opposed it in a citizen-driven, nonbinding referendum in April 2016.
The Dutch government eased voters' concerns in December the same year by negotiating a legally binding supplement to the Association Agreement with the other 27 EU member states to underscore that it will not give Kyiv the right to automatic EU membership or guarantee any EU military aid for Ukraine.
The Netherlands ratified the Association Agreement in June after both its lower house and Senate voted in favor of it earlier this year.
Related materials: Ukraine - EU