If you arrive on any flight you won't have access to the lounge on the day before departure, unless you are Platinum Elite.

I've spent the night at the Mercure more time than I can count. I generally give the KLM lounges a miss, but back when the entrance to the non-Schengen lounge was still located directly opposite the Mercure, I would usually pop in late evening to read a newspaper and have a drink. Invariably, I would only be admitted because I had arrived that day on a KL flight, and was a Plat. On the occasions I inadvertently showed my boarding card for my flight the next morning, I was initially denied entry.

Johan