My schedule is available on the version 3.0 or later.
About My Schedule
・view multiple calendars at the same time
・view OS calendars (basic phone calendar)
How to view multiple calendars
・Tap four parallel horizontal lines on the upper left corner.
・Tap "My Schedule" on the upper left corner.
・Tap "settings" on the lower right corner of My Schedule.
・Select calendar(s) to display
Related: Using OS calendar with TimeTree