Flag adjective "everyday" used in place of adverbial phrase "every day"

[hippietrail]

This has become very common among both native and non-native English speakers.
Surprisingly, the browser only detects adverb used in place of the adjective, which is less common.

This is something I do everyday. → every day (compare every night, every year, etc)
It's nothing special, just an every day thing. → everyday (meaning mundane, typical, not special)