I started working part-time when my son was about 15 months old, and I began putting him to daycare a few hours a week. He absolutely loved it from the start! He would do running movements with his feet before they touched the ground to join his friends faster, and he would actually throw a tantrum when it was time to leave...
Now he is 3.5 and he goes to daycare 3.5 days a week. He loves it so much that he misses it when he has to stay at home because he's sick! They do great activities over there, and he learned a lot of new things through interacting with the other kids.
Putting your child to daycare is not a punishment: it is a way for him/her to learn new tools, and for you to keep your sanity