We will be in SLC and have a spare day to explore the countryside. Any suggestions? My daughter is suggesting a drive out to Park City for the day. We will be in the National Parks both north and south of SLC on this trip with SLC in the beginning, middle and end.

There are many options for a day trip from SLC.

Park City is a quaint town with lots of walking and cycling trails (or ski routes depending on the time of the year of your visit). You could easily spend a day exploring the area.

Antelope Island is also another beautiful part of the world, with the opportunity to see some bison, occasional coyote, some beautiful mountain scenery and the great salt lake. This would be my recommended day trip - I loved the scenery here!

It is also possible to do day trips to the Golden Spike or Bonneville Salt Flats, though they would involve longer drives.

Other's will give you some more suggestions. Let us know what you end up doing!

I've always wanted to go to Sundance.
http://www.sundanceresort.com/

There's lot to see and do but the summer concert series/plays are of interest to me too -
http://www.sundanceresort.com/music-and-film-en.html

The day would be May 28. Does that make a difference?

Alternatively you could drive up into the Uinta Mountains. Some spectacular scenery here and option to do a few hikes if that appeals, or maybe a picnic lunch?