If it was your birthday. (Hey! It is my birthday! Happy Birthday to me!) and say you expected someone to call you and wish you a happy birthday, like for instance your mother. If she didnt call my later in the evening would you call her yourself, just to make sure you talked to her on your birthday? Or would you not see the point, after all its more the thought that counts. The actual action of taking a few minutes to stop and think "Hey, its her birthday I should give her a call".
This also applies to a best friend, so would you do something different if it was a friend rather than a mother?