Trying to help a toddler adjust to changes in a routine can be hard, but it isn't impossible. As parents who are splitting up, you may not be sure of the best way to provide for your child. Is it a good idea to live separately and to transfer them back and forth? Is it possible to use your home as a "nest" and to share it with your ex-spouse while maintaining your own separate apartments for days when you don't have custody?
Everyone who goes through a divorce with a toddler has questions like yours. Fortunately for most parents, children do adjust quickly. Explaining that they'll see mom or dad on certain days might be a little complicated to remember at that age, but telling them in the morning that today is a "dad day" or "mom day" can help your child get into the right frame of mind and prepare for the transfer of custody.
The bigger issue parents face is children who don't want to go back and forth between houses. It can be a little difficult to help your child understand a custody agreement at this age, but you can both help them get used to the changes. Work together as much as possible to make each home feel special and welcoming, so your child has less stress about being away from familiar settings.
Your toddler, like other small children, is likely to do best with a simple, structured schedule. Do your best to stick to a simple schedule as often as possible, and you'll see that they adjust quickly.