If you would like to keep the costume on the whole rest of the day, don't do anything because when it goes to bed, in the morning the costume will be off and you will no longer have it anymore. If you want the costume off NOW, then you should set the time when your tama usally goes to bed. A little while after that change the time to when your tamagotchi wakes up, or any other besides it's bedtime. Hope I helped!