Last frost date? Here, with the weather we've been having? Lord only knows. When we first moved here 16 years ago, I didn't dare set anything outside before the first week of June. Last year and the year before, I put plants out in mid-May. Actually the USDA changed our zone to 6a a couple of years ago. Maybe they're right after all.
All I know for sure is that the wasps have gotten an early start this year, forcing me and my seedlings out of the greenhouse about a week ago. That's a full month earlier than usual (if you have wasps in your area, never, but NEVER get a wood frame greenhouse!)