What is the center value, and why does the constructor need it?

[SudoPlz]

My data is this:

{ id: 1, startTime: '1015', endTime: '1115'},
{ id: 2, startTime: '1025', endTime: '1120'},
{ id: 3, startTime: '1035', endTime: '1115'},
{ id: 4, startTime: '1045', endTime: '1115'},
{ id: 5, startTime: '1215', endTime: '1415'},
{ id: 6, startTime: '1135', endTime: '1515'},
{ id: 7, startTime: '0935', endTime: '1014'},
{ id: 8, startTime: '0935', endTime: '1614'},

and I have no idea what to use as a center value.

All I want from this library is a fast way to create trees, in order to be able to tell if a new interval overlaps with the tree. (That's all I want, I don't even want to know WHICH one overlaps with the tree)..
Any ideas?

[tvedtorama]

I think this is because this implementation is a Centered Interval Tree (Wikipedia). If that is correct, you actually have to select a good center, such as the median of all interval centers - before packing in your data.

Disclaimer: Haven't checked the code - which is soaked in coffee.