The fact that there are two kinds of municipally-run public day care facilities, hoikuen and kodomoen, is another example of how the deeper you get into the day-care system here, the more confusing it can become. Both hoikuen and kodomoen are public day cares, or ninka (for an overview on the ninka system, click here), but there’s some differences in the way they’re run.
The hoikuen system is what most people are familiar with as it’s the long-established day-care system, while the kodomoen system is relatively—facilities knowns as kodomo-en have been popping up more and more over the last few years, and the governments seem to be leaning in the direction of transitioning to kodomoen altogether, although it will still be a while before that happens. The kodomoen are public childcare facilities and are very similar to hoikuen, but their organizational structure differs slightly from the hoikuen system.
The basic difference is that kodomoen have been designed to integrate hoikuen and youichien under one roof. Youchien refers to the (non-mandatory) nursery school or pre-school system here, which children are enrolled in from April of the year they turn 4. It’s a half-day pre-school program, geared at families with one stay-at-home parent. This is not day care, but pre-school. The kodomoen, I think in an effort to somehow streamline government funding, offers two types of courses at one facility: a day-care course and a pre-school course. The day-care course is offered from newborn age, while the pre-school course is offered from April of the year your child turns 4. Again, these are separate courses but in the same facility.
In addition, the kodomoen facilities also usually have some kind of community outreach program. In an effort to be more involved in with families in the surrounding neighborhoods, many kodomoen offer scheduled times when they’re open to the public for parents with kids to come enjoy song-time or another especially arranged event or class. (I think you have to be a ward resident to join these free activities. You can pick up a monthly schedule of activities by visiting your local kodomoen.)