I don't think there's any way to do what you're asking, specifically.
Here's a hack that would work, tho... You could schedule your process twice in
your crontab -- once at gmt-7 and once at gmt-6 (I think those are correct for
Mountain time), i.e. midnight GMT standard and daylight times. Then, have your
process check to see if it's midnight GMT, and if not it should bail. That way,
each of those cron entries will work for half of the year.