Our weekly group ride every Thursday is an hour, but while there are some routes where we can fairly adequately pick the appropriate distance (usually 34,000m) to roughly last 60 minutes, any time we change routes (especially if the elevation profile changes) there's no great way to determine how many laps or how much distance we should use to set for the duration. We should be able to create Group Rides that last 30 minutes, 60 minutes, or any other arbitrary amount of time rather than just by distance or lap count. The function is already available as a field in Time Challenge, but it should also be an option in Group Rides.