I tested this fix on https://trunk-mysql.nightly.sakaiproject.org/ by creating a site with the Sign-up tool, creating a new sign-up with a notification to the meeting coordinator. I became a student in the roster and signed up. The event was for May 25, 2017 from 8:00 am - 5:00 pm EST. Here is what was in catalina.out:
24-May-2017 18:22:36.560 INFO [http-apr-18888-exec-3] org.sakaiproject.email.impl.BasicEmailService.testSendMail sendMail: attachment name: 1842b61f-8660-4c45-948a-7679d2741c45.ics type header: text/calendar; charset="utf-8"; method=REQUEST; name=signup-invite.ics body:
BEGIN:VCALENDAR
PRODID:-//trunk-mysql.nightly.sakaiproject.org//Sakai External Calendaring
Service//EN
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:REQUEST
BEGIN:VEVENT
DTSTAMP:20170524T222236Z
DTSTART:20170525T080000
DTEND:20170525T165959
SUMMARY:Test for UTC and Outlook
TZID:America/New_York
UID:1d9d614c-2348-4702-9909-c573bffa07ca
SEQUENCE:3
DESCRIPTION:-------Note that rejecting calendar invites does not remove you
from the event. Please return to the site to make any modifications.
LOCATION:Bostock 024
ORGANIZER;CN=The Instructor:instructor@example.edu
URL:https://trunk-mysql.nightly.sakaiproject.org/portal/site/4a8fa47b-4128-
4c82-8228-ca8451374db1/page/e381ee65-cbc4-475f-838a-0f9df8d95737
ATTENDEE;ROLE=CHAIR;CN=The Instructor;PARTSTAT=ACCEPTED;RSVP=FALSE:i
nstructor@example.edu
ATTENDEE;ROLE=REQ-PARTICIPANT;CN=Zachary Anderson;PARTSTAT=ACCEPTED;RSVP=FA
LSE:za@example.edu
END:VEVENT
END:VCALENDAR

I created an .ics file with this information and imported into Outlook and it created an event with the correct day and time.

Depends on https://sakaiproject.atlassian.net/browse/KNL-1480#icft=KNL-1480 to be able to test this in the UI