OSIS-59 Fix start_year bug for externals
OSIS-59 Fix start_year bug for externals

uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis_louvain,uclouvain/osis_louvain,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/osis,uclouvain/osis_louvain,uclouvain/OSIS-Louvain