Confirmed but I am unsure if it is also for the Schengen lounge?
KLM’s non-Schengen Crown Lounge peak hours are:
Mornings: daily between 7.30 and 11 am
Evenings: not applicable
KLM’s Schengen Crown Lounge peak hours are:
Mornings: daily between 7 and 10 am
Evenings: Thursday and Friday between 7 and 9 pm
Guests of Flying Blue Platinum, Flying Blue Gold and SkyTeam Elite Plus members are only accepted outside peak hours
Guests of Ultimate, Skipper and C2000 customers are accepted