Just wondering

Hi moms so I'll be a first time mom in December And I was told by my sister In law said you need to have a not pad to write down what time your little one pooped peed and ate at. Has anyone else use this method?? And if so did it work I'm just a little worried about it because what if ur little one don't go to poop the same time everyday I don't wanna be stressing over it. So has any other mom write down what time your baby ate pooped or peed??