Unfortunately it's not possible to change the delivery date. You could reach out to Spotify Support so they can refund the payment and you then can buy another gift card. The person you sent the Gift Card to will receive an email on both dates, which can be a bit confusing because they would only be getting one eCard:
If you get an automated reply email telling you to check the Knowledgebase or the Spotify Community, you need to reply back to it, even if it's from a no-reply address. Spotify Support usually replies within 24-48 hours.
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