Enrol earlier will be better. Baby not so scare and more socialise and talking will be faster. I enrol my first boy after 2 years old while my 2nd son at 18months really have different in their speech and learning, didi tends to catch up more fast and not scare
Childcare centers can have very very long waiting list depending on the demand, some can have up to a year's wait list, so you can start checking and registering your interest now in this website https://cms.ecda.gov.sg/preschool