Problem with start time to interval (interval-start x interval-minutes)

[ldurans]

For a legitimate bug, in order to process faster, please go here https://codepen.io/Hawkeye64/pen/RwwwKQL, fork the codepen, add code to reproduce the bug and submit link here (don't forget to save your codepen):

Describe the bug
By setting interval-minutes the calendar loses the interval-start ability.

To Reproduce
Steps to reproduce the behavior:

1. https://codepen.io/ldurans/pen/jOxZGQv
2. :interval-minutes="20"

Expected behavior
Start Time-Sensitive Interval