Upvote:1
The question is based on a wrong premise: my visa is in fact valid from an earlier date.
I was fooled by the "annotation field" in the visa, which states the dates of my program. The person at the embassy I spoke to said that one may enter up to 30 days before and exit up to 30 days after the program.
If someone has the same question but with a correct premise, I'd be happy to open this question again!