April, May, June and August. Are other month names in use anywhere? Specifically December: it seems so obvious in a historically Christian community, but perhaps other names like Noel and Holly are more user-friendly?
In South Africa a lot of month names appear as surnames in the 'Coloured' community: mixed-race people often with slave ancestry, and the slaves came from elsewhere in Africa and also the Pacific islands so the month names were presumably the month in which they arrived here and were sold. The ones I see most often are February and September, but there are others.