Mavericks Calendar appointments showing wrong time

My wife's 27-inch Late 2012 iMac running 10.9.5 has problems with Calendar invites from a specific business client. The invites once accepted into Calendar show two different times - one listed as EDT and one EST - and the Calendar itself decides to show the wrong time (1 hour later than it should). I've double-checked that the Time Zone settings in System Preferences are correct for the Region and time of year (EDT), and the Time Zone Support is turned on in Calendar Preferences.

Other calendar invites from other people are fine. The Business client in question is using LOTUS NOTES, but a test invite sent to my own computer (running Yosemite 10.10.3) from the Business reads correctly, and the same invites my wife has previously received read correctly in the MS Outlook for Mac calendar. The Business' IT dept. did notice that the Mail Host's server (service with HostGator) is set to CST - 1 hour off, but I don't see why that would be the problem when the invites still read correctly in other Apps and Operating Systems...

Others have encountered this with the Mavericks Calendar. Is this a Calendar bug? Anyone with suggestions on how to beat this?

I don't use Outlook on my own computer, but the issue for her is that the Apple Calendar isn't displaying properly - I launched her account in Outlook on her iMac just for comparison, and to narrow down the nature of the problem. The problem appears to lie with the combination of the invites and her Calendar app or just her Calendar app. I'm wondering if anyone else that has encountered this with their Mac has found a solution? (Since a glance online reveals that other folks have experienced this problem)

If I recall correctly, I remember something being changed in Mavericks Calendar appoints to be able to show multiple time zones, so maybe do some more searching and something like these might help:
Get Your Calendar Items To Show Their Time Zone In Mavericks Beta [OS X Tips] | Cult of Mac
Enable Time Zone Support in Calendar App for Mac OS X | OSXDaily

It I recall, there was something to set for travellers and to avoid time conflicts. It may even be in the Calendar "Help" section as to proper settings.