It's whenever you want!
Regarding the exact date, there are two possibilities, depending on your situation:
- You are not yet insured: choose the date you want to be covered (tomorrow if you wish 🚀)
- You are already insured: count 34 days, so that we can respect the legal notice period with your former insurer (which is 30 days), and the additional 4 days leave us the time to contact them by a registered letter 👌