I don't think that there is any one perfect time for meetings. There will always be conflicts for some and others won't care what time it is because they won't attend anyway.
Our council meetings are held at 6:30pm, last year on Wednesdays but that will be changing this year. We as a board, chose that time because 1. One of our officers lived in Fernley (45 minutes away on a good traffic day) 2. It gave the 5 o'clock workers time to get home, feed people and make the meeting. 3. 6 O'clock workers couldn't feed anyone but could still make the meeting on time.
We had no board members or delegates, that during the planning meeting, expressed that this time was a problem.
At my school, for two years, the meetings were held at 6:00pm. There was a good number of parents who stayed home during the day but the time worked okay (meeting attendance always fluctuates between low and slightly higher, unless there is a problem) This last year, they alternated between 3:30pm (school gets out at 3:15) and the other month, 5:30pm. There was no change in past year's attendance, nor between the months.
Other units I have, their meeting times also vary. I know that at least two of them have them at 9:00am (I have been to their meetings) and again, the attendance numbers have been the same. I have also been to one unit's meeting that was during the lunch hours (12:00pm) again, no difference in attendance.
If your focus is on getting more attendance at the meetings, either from parents, teachers or both, you need to survey them and see what works in their schedules. This does not, however, guarantee that they will be there!
Another important note for our area, we are a 24 hour town/area and we have many casino workers who do the swing shifts or graveyard. For some of them, 10pm would be the best.
I think the best thing to do is to accomodate your officers and their schedules. They technically have to be there.