Looking at ordering our 'save the dates' do they just go to day guests? we are getting wed next summer holiday, when is best to send them (I am a teacher myself!)
I would send them a year to six months in advance and yes, to day and evening guests.
They really need to go to anyone you want to save the date.
I would say that generally it's just the day guests, especially if they will need to take time off work for a weekday wedding etc. Evening guests are a different matter as even if they work they should be free in the evening? As for sending them I'd say a year in advance, particularly if it's during popular holiday months as people often book holidays 9-12 months in advance. Hope that helps?