Craft a heartfelt and timeless gift with this unique ChatGPT prompt. This prompt assists you in crafting a customized letter for a baby. The letter is intended to be opened on the recipient's milestone birthday, be it their 18th or 21st, making it a beautiful time capsule of love and wisdom. This prompt is perfect for parents, grandparents, aunts, uncles, or godparents looking to give a meaningful and enduring gift that grows in value with time. Adapt it to your needs and create a remarkable keepsake that will be cherished for years to come.