The Eurydice network has been collecting data on instruction time for more than two decades. These data have been published in many Eurydice publications, notably all editions of the 'Key data on Education'. Since 2010, annually updated data on instruction time has been available on the Eurydice website. Since 2013, the Eurydice network has been collecting jointly with the OECD (the NESLI network) data on instruction time. For many years too, the OECD has been collecting such data through the INES network for the collection and adjudication of system-level descriptive information on educational structures, policies and practices (NESLI, previously Network C). Given the great similarities between the two data collections, the OECD and Eurydice networks have decided to produce one single data collection tool and conjointly manage the data collection on instruction time. This common work avoids inconsistencies and overlaps between similar sets of internationally comparable data. The first section defines the scope of this publication and provides relevant definitions. The second contains a reading guide to the national data sheets (diagrams). This guide briefly explains what the diagrams show and how to read them, and lists the acronyms and abbreviations they use. The third provides country specific notes complementary to the information provided in the diagrams. These diagrams are located in Part II (Instruction time by country) and in Part III (Instruction time by subject). The annexes include diagrams on instruction time for subjects or curriculum categories that are only present in a small number of curricula in European countries (i.e. instruction time for the third and the fourth foreign languages as compulsory subjects and for the non-compulsory curriculum).