At around age 6, the Date Place will be added to the locations on the door icon menu. When you select it, your Tama-Go will travel to the Date Place where s/he will meet a potential mate. You'll then be asked whether you want your character to marry that one. If you select Yes, they get married. If you select No, your character returns home. As far as I can tell, your character can visit the Date Place as many times a day as you like... however... regular adults (such as Mametchi, Kuchipatchi, Memetchi) are offered only during the first three visits of each day. Beginning with each day's fourth visit you'll be offered only Otokitchi or Ojitchi (depending on the gender of your character.)