Two weeks ago I posted a story about KB 3114570, the Outlook 2010 patch that fixed the botched KB 3114409 but introduced (or re-introduced) some very odd behavior. The patching details are complicated -- see the story -- but the new behavior is pretty straightforward.
Poster Jon999_ in the Microsoft Answers forum describes it succinctly:
After the [new KB 3114570] update is installed, Calendar appointments that span midnight (ie, appointments that start on one day before midnight and end the next day after midnight) appear in Day and Week calendar views as if they were all-day appointments, as a small bar at the top of the day column instead of covering the appropriate hours. Additionally, the end time of such appointments shows up wrong (as 00:00, regardless of the actual end time) in all views including Month view. Prior to this Update, such appointments of <24 hours duration appeared as expected, covering the appropriate hours. Uninstalling this update removes the error.
There were additional problems for Windows 10 users because Win10's lovely forced update feature made the uninstalled update re-install itself over and over.
Last week, in the same thread, Microsoft employee Gabriel Bratton dropped something of a bomb. He explained that the observed behavior wasn't a bug but a feature:
I wanted to post and let you know that the change you are seeing is intentional and was made based on customer feedback to improve the product. The request was to change appointments that span midnight to show as a single appointment spanning the two days rather than two separate appointments in the week and month views. This change is also being forward ported to Outlook 2013 and Outlook 2016.
I am following up on your point that the appointment bar shows as ending at midnight. There were some other minor refinements still being reviewed and I will update you after I find out if that will be changed.
The announcement was met with some consternation on the site. Jon999_ shot back:
Because of my business, I frequently work night shifts and have meetings that span midnight in my time zone. Not being able to see my meetings on an hourly basis makes the calendar view practically useless.
I also travel transcontinentally or internationally often, with meetings in different time zones on the same day. Having my overnight flights show on the timeline is crucial to making sure that the meetings I schedule on arrival the next morning or between flights don't conflict with the flights. For example, I need my 10 p.m. EST to 6 a.m. GMT flight to show up on the timeline covering those hours so I can see instantly that if I schedule a teleconference at 6 a.m. CET, it's not going to happen.
Poster ShunzhouGu chimed in:
Option this behavior, PLS! It screwed up the outlook calendar and bothered hundreds of colleagues here in my company, who need to work overnight with global teams.
Bratton's statement that the change is being "forward ported" to Outlook 2013 and 2016 may give you pause as well.
If you use Outlook 2010, 2013, or 2016 to keep track of appointments occurring around midnight, it would behoove you to drop by that Microsoft Answers forum thread and weigh in.