If you put the date here, staff or someone will do it for you. It takes special formatting and you can't add it to the main page like you are trying to do.
This sounds like you are trying to add an episode to the main TV-series page which is not supported, sorry.
Please add the release information to specific episodes, for example, if you add the date to the pilot it will be reflected on the main series page -> http://www.imdb.com/title/tt5734500/
Before I do this, please can you confirm that the first episode of 'This Is Us' was released in Portugal 3rd March 2017? Once you have confirmed this I will be happy to make the necessary changes to this episode.
