I've been told of flexibility by a) the Lone Pine permit station, and b) rangers (including those checking permits) on the trail. Nobody has any interest in you forcing a dangerous pace/pushing through bad weather etc. and they are very pragmatic on this. Indeed, once the permit office issued me an exit permit that was knowingly a day wrong, and told me not to worry about it.
I've twice exited a day wrong (once earlier, once later), been checked, and had no issue.
Furthermore, in my experience, the Lone Pine permit office has total inconsistency/a lack of knowledge/clarity of the actual rules. I've been told that the permit date is the day you cross the crest, the day you summit, the day you leave the wilderness, the day you finish... I appreciate for some people these can be the same, but if you're hiking slowly, with kids (as I was twice), then they can be different. Camp up at the MWT/JMT junction, summit and cross crest next day, camp at Consultation Lake and exit the following day is a typical pattern for me.
Edited by britonwhit(ney) (01/29/20 04:58 AM)