10th century (2nd half) - Edification of the Castle of Arnoia, according to tradition;
1064 - First documented reference regarding the fortification;
1092 - A document mentions the properties of Celorico and Terra de Basto;
12th-13th centuries - Second occupation period of the Castle and edification of the Castle of Arnoia's Romanesque structure ;
1717 - The parish seat is transferred from Vila de Basto to the parish of Britelo;
1726 - The Terra de Basto was by then divided into two municipalities, Celorico and Cabeceiras de Basto. The Castle of Arnoia's keep still showed its crenellation crown;
1758 - The Castle of Arnoia was already presenting some traces of ruin;
1946 - It is classified as a National Monument by Decree no. 35,532 (Governmental Gazette no. 55, from March 15th);
1960-1963 - Period of restoration works in the Castle of Arnoia, under the responsibility of the DGEMN – Direção Geral dos Edifícios e Monumentos Nacionais [General Directorate for Buildings and National Monuments];
1985 - The Castle of Arnoia is attached to the IPPC – Instituto Português do Património Cultural [Portuguese Institute of the Cultural Patrimony];
1992 - The Castle of Arnoia's jurisdiction is transferred to the IPPAR - Instituto Português do Património Arquitetónico [Portuguese Institute of the Architectonic Patrimony];
2002 - Archaeological surveys were carried out inside the fortification;
2004 - Installation of the Interpretive Centre of the Castle of Arnoia;
2005 - The Castle of Arnoia is reallocated to the IGESPAR – [Portuguese Institute for Management of Architectural and Archaeological Heritage];
2010 - Integration of the Castle of Arnoia in the Route of the Romanesque;
2014 - Improvements to the surroundings of the Castle of Arnoia, under the scope of the Route of the Romanesque;
2015 - Intervention for the conservation and protection of the inside and outside of the Castle, under the scope of the Route of the Romanesque;
2020 - The Portuguese State transfers the responsibility of management, promotion and conservation of the Castle of Arnoia to the Municipality of Celorico de Basto;
2024 - Conservation work on the Castle and its surroundings promoted by the Municipality of Celorico de Basto.
