Date accurate to within a week or so. This one has bothered me for years. I was down low on the sand, trying to photograph a Tiger Beetle, when I found this moth. The pattern matched, precisely, the color of sand on this beach. The moth was closely associated with decaying kelp, hanging about with what I presume were kelp flies, Coelopidae. (I did not photograph the flies, not doing diptera at that time, unless they were large and colorful.) I am guessing (!) that the caterpillars feed on the decomposing kelp. I just can't imagine a reason for a moth to be out on the beach during the day, near a bunch of decaying seaweed, unless it was going to find a mate and/or lay eggs right there. There were dune plants higher up, but this was right down near high tide line near the decaying kelp. I don't think I've ever seen a moth down on the beach before or since.

OK, thanks for comments. Looks like a geometer. I like Entephria on that plate of Canadian moths linked in comments. Here's a species confined to coastal habitats in the UK. Interesting. Several other genera look close as well in that plate from Moths of Canada.
Other similar genera/species from that source: Perizoma basaliata, Rheumaptera spp.

This moth was in coastal Northern California, quite similar to habitats of coastal Vancouver, so it might be found in Canda too.
Updated photo posted 2/2/2015! I had originally estimated the wingspan here as 35 mm, but that is too high--more like 25mm is reasonable, as 35 mm is quite a large moth.