It seems it was spread out in different ways over time- you can read various amendments to the '90 directive that started to make specific things mandatory instead of optional in the opening parts of Directive 1999/10/EC [1] - there had been amendments for specifics on sweeteners and such before, and in '99 a few more things mandatory depending on claims by the manufacturer it seems...
but as far as I can tell there was no obligation in Europe to have the level of detail about fats, sodium, etc. like the US's labels had until even later- maybe 2006? [2] and there was the last major change it seems in 2011 which is what is still essentially in place today. But yeah, it seems like the level of information made mandatory and not optional wasn't like it is today until around or maybe slightly after the Millenium.
but as far as I can tell there was no obligation in Europe to have the level of detail about fats, sodium, etc. like the US's labels had until even later- maybe 2006? [2] and there was the last major change it seems in 2011 which is what is still essentially in place today. But yeah, it seems like the level of information made mandatory and not optional wasn't like it is today until around or maybe slightly after the Millenium.
[1] [PDF] https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:...
[2] https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02...