In time I offered more than one bounty on the same question. But on my profile page it looks like I offered these bounties all on the same day:
The date you see there is not the day you posted or awarded the bounty. It corresponds to the latest activity on the question, which is an edit on this answer. In the question in between, it is the day the bounty was posted, because that actually counts as 'activity' on a question.
This behaviour is consistent with other tabs in your profile, e.g. the list of favourite questions.