The World Association for the Development of Philately (WADP) and the Universal Postal Union (UPU) jointly conceived and developed the WADP Numbering System - WNS, which was launched on 1 January 2002.

XI001.07

Country / Post Montenegro
Date of Issue 4 January 2007
Primary theme Science & Technology (Time measurement)
Subject 425 years from the date when the Gregorian Calendar was introduced
Width 42.0 mm
Height 35.0 mm
Denomination 0.50 €
Number in set 1
Layout/Format sheet of 8
Perforations 14 by 14
Stamp issuing authority Montenegro Post
Printer FORUM, Novi Sad