There's nothing romantic than purposing a girl on her birthday. Because every girl wants to feel over the world on her birthday. She finds it very curious that what her boyfriend has arranged for her. And also she wants to tell the whole world about her relationship with this particular boy, with whom she promises to live a life long journey.
Now, when the boy comes with the idea of purposing a girl on her birthday, so he should keep many things in mind like whether his family will accept her, how her family will treat him after the relationship, what are the financial positions of both, etc. If he has gone through every detail that might be helpful in the long run. And he thinks that the results are being positive, he will definitely go for it and purpose her girl on the birthday. He could arrange a surprise party for her, inviting all her family members as well as his own, and purpose her in front of everybody. This Moment will stick in her mind and keeps on flashing for the rest of her life.