Change minimum duration to something other than 30 minutes

When scheduling an event in iCloud calendar, can you set the minimum duration in the pull down menu for "from" to something other than 30 minutes?

For example, if you schedule an even at 9:00 AM, the shortest time available in the pull down down menu will read "9:30". I know I can manually type any time I want, but I was looking for a way to change the default options.