Really, for me best, or possibly the only reliable time I can participate, is day time during the week. At work it is easy for me to sneak off into a call. At home it is quite random due to kids and other family timetables. But I guess for the people in US that is an impossible thing due to time difference :)
Voted for saturday, sunday or monday evening. Fridays are unfortunately out due to usually going out with either colleagues or friends.
But tbh, I'm personally more interested in following discussion through other channels, calls are imho not a very efficient way to discuss things. The most vocal person will just hold the most power ;) So maybe don't hold my votes in the doodle that high when deciding a time.