Help me figure out the name of this song will you please?

Ok some of you are great at this, so hopefully you can help me....I love this song, but don't know the name.... It is a new song that they play on like the "alternative rock" type stations or Indy rock type stations i guess. Its like a modern day country sounding song. There is both a girl and a guy singing there own parts, and part of the chorus has a lot of whistling. The name might be something to do with "last night", or "saturday night" maybe. I know this is a biiiiig stretch, but hopefully some master of music out there can help me.