Outlook Calendar

Maintaining Calendar Coherence
Two of the most popular (or at least the most used) features of Exchange Calendar are the ability to set up recurring meetings, and the ability to delegate tasks to others. When used carefully, these are extremely helpful tools. However, when used without understanding what Exchange is really doing, issues may occur. 
The following will guide and clarify the functions and use of Exchange Calendar in Outlook 2013.
Using the Exchange Calendar
When a meeting appears on your calendar and a coworker's calendar, you may be under the impression that there is a single calendar entry. 
Each person’s calendar has a copy of the meeting invitation. As you accept invitations, updates, and cancellations, the item on your calendar is updated. Your coworker does the same. As long as you each receive every change to each meeting, each calendar entry gets the same updates, and this why there appears to be a single calendar entry.
If one of you misses an update, the copies no longer look identical. The meetings start looking different, and it appears that the calendar function is experiencing issues. 
Calendar Messages
Calendar updates are sent by email messages. Make sure that everyone sees the same view of a meeting by sending and processing every update.
As the meeting organizer, send notifications to all attendees on every change. Keep everyone synchronized by sending all updates to all attendees. For example, Outlook, Outlook Web App (OWA), and some other email/calendar clients give you the option to only notify the attendees that you've added or removed. To keep all calendar meeting information, include everyone, every time.
Include a note about what the change with each update. This ensures all attendees are informed and attendees don't skip updates that they think they have already seen.
As a meeting attendee, accept or decline every calendar message. If you delete these, you may miss important changes to the meeting. If you accidentally skip one, you may go back into your Deleted Items folder and accept it.
Send a response to the meeting organizer when you accept or decline. 
Some email/calendar clients allow the meeting organizer to choose whether to ask for acknowledgment. If the organizer doesn’t need to know who is attending, it’s okay not to use this option. For example, if you use all-day events to notify your group about vacation days, your co-workers do not need to “accept” your vacation. Similarly, if you’re inviting many people to an optional meeting and you don’t need to know how many plan to come, you can safely use the “no response required” option. 
The number of messages that are sent with no response appear to be the reason calendar issues may exist. Fortunately, you can use your Exchange email client to filter all meeting request messages into a folder automatically.
If you use this method, check the folder frequently so you don't miss meeting invitations and updates.
Choosing and Using Calendar Options
The most consistent results are with Outlook 2013 (Windows) and Outlook Web App (any current major browser, any current operating system). Outlook 2011 (Mac) trails its Windows cousin in stability. iCal (Mac) works for the simpler cases, but consider switching to Outlook Web App to set up or manage a complex meeting. 
Mobile devices create the most problems: they are best used for reference only. You can set up personal appointments on a mobile phone, but propose or accept meeting invitations on your computer. In general, the more complicated or more detailed the task, the more important it is for you to use Outlook (for Windows) or Outlook Web App (Windows or Mac).
Using Delegate Access
If you have an assistant manage your calendar, do it consistently. If your assistant creates and accepts meetings for you, always do it the same way. This leads to more consistent, predictable scheduling. Try to have no more than one delegate who can update your calendar. And try to have everyone involved use the same email/calendar client when updating and viewing the calendar.
If you have given delegate access to someone, don't make or accept meetings on your own. This often leads to calendar conflicts. For more information about Delegate Access, contact the ITS Help Desk.
Recurring Meetings
Do you have one of those meetings that has a different time and location and agenda each week? If you use the recurring meeting feature for this kind of meeting, you're likely to start seeing problems. Only use the recurring meeting feature if the time and place are the same each week.
If you need to change the time or location for one date in a recurring meeting, cancel that occurrence of the meeting and send out a new invitation for the alternate time as a single, non-repeating meeting. Send out the weekly agenda as a separate mail item, not as a meeting update.
Each exception to a meeting series is stored in the meeting notifications that are sent to all participants. As those lists of exceptions get longer and longer, errors creep in and schedules get out of sync. Keep your repeating meetings simple and predictable. 
Apply Updates
Vendors do fix problems with their email/calendar clients. Some of the fixes have had major impact. Apply all updates to your email/calendar clients to keep them working smoothly. That includes your computer as well as your mobile phone or tablet. Mobile email/calendar apps have had a number of synchronization issues fixed in the past several years; make sure you have those updates applied.
Time Zone Setting
Each email/calendar client has a time and a time zone. The time zone you have selected is displayed to meetings you set up, and the email/calendar clients of people you invite will try to match that to their own time zone. Mismatched time zones can end up with shifted meetings.
Make sure that your email/calendar client is showing the correct time, and has the correct time zone. Sometimes the email/calendar client has a time zone setting in addition to the operating system's time zone. Make sure those are both in agreement.
Mobile devices have time zones, and sometimes can change the time zone automatically as you travel. Finally, Outlook Web App has a time zone setting as well. Make sure that is set in agreement with other settings that you use. Make sure that your email/calendar client knows when Daylight Saving Time starts and stops. 
Scheduling Rooms and Resources
You may be responsible for scheduling a meeting to a resource (meeting room) calendar. The best practice is to invite the room/resources to the meeting via the "Rooms" button in the appointment window.
You should check the scheduling assistant to be sure the resource is available. If the room is booked, find another room that's available, then send the invitation. Make sure you get an acknowledgment from the resource that it has been accepted. Follow this path to reliably reserve rooms for your meeting.