Telephone numbers in the German Democratic Republic

Before German reunification, West Germany (including West Berlin) used country code +49 and East Germany used country code +37, each with its separate area codes and telephone networks. Calls between the two countries required international dialling, hence 0037 to call East Germany from West Germany,[2] and 0049 from East Germany to West Germany.[3]

On 1 June 1992, all area codes were brought under the +49 code.[4] This had introduced on 15 April, with the old and new codes running in parallel.[5] East Berlin's 02 area code had already been brought under the 030 (the former West Berlin) area code.[3] All area codes (except Berlin's) had a 3 inserted into the code (e.g. Erfurt's former 061 area code[6] became 0361).[7] Sometimes, the code would be changed entirely.

The +37 code was then freed up to be used by many of the newly independent states which were created following the collapse of the Soviet Union, which had previously used that country's +7 code (e.g. Lithuania adopted the code +370).[8] Some European microstates which had previously used the networks of the countries surrounding them also took on +37x codes, for example, Monaco adopted +377, replacing the code +33, which it had shared with France.[9]