My aunt would always say "hezky den" when saying goodbye on the phone - was she meaning, more literally, "have a nice [weather-wise] day" rather than "have an agreeable/pleasant feeling" day? The usage in phrases like "to je hezke mesto" makes sense, but the meaning in "hezky den" confused me - perhaps this isn't as universal of an expression, or just another one of my aunt's quirks...?
It is quite common. But these are set phrases, do not examine the details of each word. This sentence here is about girls, not about a day.