Hello @echurch ,
This will largely depend on the demographic of your contacts, and a number of other factors. You can typically determine the best day and time to send an email, based on prior data about open dates/times.
In my experience, religious communications tend to perform better either in the middle of the week (e.g. Wednesday evenings), or the day before / after services. What guarantees the best open rates is consistency. Once you select a day/time, it's best to stick to that so your contacts will know when to expect it and will be sure to check their email inboxes.