API last_modified_time doesn't work?

API last_modified_time doesn't work?

Hi! I'm using the API with the URL:

https://books.zoho.com/api/v3/salesorders?authtoken=XXXXXXXXXXXXXXXX&organization_id=XXXXXXX&last_modified_time=2017-01-30T19:01:01-0123

It's my understanding that this should only return Sales Orders which have been modified on or after January 30th, 2017 at 7:01:01. However, I'm getting lots of results that have a last_modified_time that is before this date (for example,  2017-01-30T18:56:05-0500). Is this a bug, or am I misusing the API?

Thanks!