The ISN is built with certain default settings to be used by you as a general guideline, and these default settings can be changed in order to meet your company's needs. The ISN allows you to customize your Company Settings, and one of these settings is the start and end time of your business day and the format that will appear on the calendar.
In your ISN, navigate to: Settings -- Company Settings. From there, scroll towards the bottom of the page and you will see the Work Hour options that are available to pick from as well the format that will appear on the calendar. Not only the start and end times that will show on your calendar but how large a time slice you want to appear on the calendar.
Make sure to click Save Settings when you're finished making changes!