[Answer]-Easiest way to concatenate two QuerySets same Model (no order needed)

Instead of concatenating you can use Q objects and combine them with |

events = Events.objects.filter(Q(date__day=day,is_weekly=False) | Q(date__day=day%7,is_weekly=True))

If you simply want to concatenate in any order, then you could try something like this:

events = normal_events | weekly_events

Which is very similar to what you wanted to try initially.