The World Weather Research Program (WWRP) and World Climate Research Program (WCRP) have launched in 2013 a joint new research initiative, the Sub-seasonal to Seasonal Prediction Project (S2S) which main goal is to improve forecast skill and understanding of the sub-seasonal to seasonal timescale, and to promote its uptake by operational centres and exploitation by the applications communities. A main deliverable of this project is the establishment of an extensive database that contains sub-seasonal (up to 60 days) near-real time forecasts (3 weeks behind real-time) and reforecasts (sometimes known as hindcasts), following the work started with the THORPEX Interactive Grand Global Ensemble (TIGGE) database for medium-range forecasts (up to 15 days) and the Climate-System Historical Forecast project (CHFP) for seasonal forecast. Detailed informations on the database are available here. This research database, hosted at the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Chinese Meteorology Administration (CMA) is now available to the research community from the ECMWF data portal.