ARCHIVED: Indiana's adoption of Daylight Saving Time and its effect on Microsoft Exchange

This content has been archived, and is no longer maintained by Indiana University. Information here may no longer be accurate, and links may no longer be available or reliable.


In accordance with recent decisions made by the Indiana State legislature, Indiana will begin observing Daylight Saving Time (DST) on April 2, 2006, at 2am.

This change will require Indiana companies and residents to change their clocks. All clocks, including those on your wrist, on your walls, and in your computers, will need to be adjusted to reflect the change in your county's time. You may also need to change calendars and electronic calendaring devices. You will need to review your calendar(s) and identify any appointments, reminders, or tasks that are affected by the time change. Once you have identified the affected items, you will need to adjust the start and stop times accordingly.

The information in this document is intended to help those who use Microsoft Exchange as their calendaring system. The document describes several possible ways to identify and adjust affected Exchange calendar items. (At Indiana University, you can find help with adjusting your computer's time and your Exchange calendar in the Knowledge Base document ARCHIVED: At IU, how does Indiana's adoption of Daylight Saving Time affect my computer, PDA, or telephone?)

How Exchange calendaring works

Exchange stores times in UTC (Coordinated Universal Time, also known as GMT [Greenwich Mean Time]), not the actual local time you set for the appointment. This applies to tasks and reminders as well as calendar items. Appointments display on your calendar according to your chosen local time zone by applying an offset to UTC to reflect the correct regional or local time:

Time zone Offset from UTC
Indiana (East)
GMT -0500 (Standard) / GMT -0500 (Daylight)
Eastern (US & Canada)
GMT -0500 (Standard) / GMT -0400 (Daylight)
Central (US & Canada)
GMT -0600 (Standard) / GMT -0500 (Daylight)

Contrary to the misperception that Indiana changed time zones twice yearly, most of Indiana was always on Eastern Standard Time (EST) and never shifted to Eastern Daylight Time (EDT):

  Indianapolis New York Chicago Denver Los Angeles
Daylight 12pm 1pm 12pm 11am 10am
Standard 12pm 12pm 11am 10am 9am

Most of Indiana will now follow the rest of the Eastern time zone and shift from Eastern Standard Time (EST) to Eastern Daylight Time (EDT) every April:

  Indianapolis New York Chicago Denver Los Angeles
Daylight 12pm 12pm 11am 10am 9am
Standard 12pm 12pm 11am 10am 9am

The challenge

Most computers in Indiana have been using a special Indiana time zone setting, (GMT -5:00) Indiana (East). In order for your system to properly adjust automatically for observance of DST, you will need to reset your computer to one of the standard Eastern or Central time zone settings.

When you adjust your computer to (GMT -5:00) Eastern Time (US & Canada) with the Automatically adjust clock for daylight saving changes box selected, all your appointments during DST will move to an hour later than you originally scheduled them. Additionally, your all-day appointments may now cover multiple days.

You will experience a similar problem if you move to (GMT -6:00) Central Time (US & Canada) with the Automatically adjust clock for daylight saving changes box selected, except your appointments that fall during DST will be set an hour earlier. You may also find that your all-day appointments cover multiple days.

Confusion may result. Failure to correct your calendar can result in missed appointments, wasted time, and disruptions in your work.


The best solution is to adjust all your individual calendar entries on all Exchange Server calendars to the correct time zone (Eastern for most of Indiana, Central for certain counties; for more information, see the Knowledge Base document ARCHIVED: Time zones in Indiana). You will need to take into account all meeting attendees and resources. Meeting organizers must send an update for corrected meetings, in order to keep proper linkage to all attendees and resources.

When entries are updated this way, the proper UTC is stored with each appointment; this is critical to ensuring the proper offset for Standard and Daylight time periods.

The ideal solution

Calendar items are complex enough that the calendar owner or delegate needs to examine each one to determine if changes are needed. Ideally, you'd use custom or client search tools to find the items that need to be changed. Once the owner of the calendar has examined them and confirmed necessary changes, then an ideal solution would facilitate making those changes in batch.

The manual method

Although time consuming, manual changes are the only way to ensure that appointments are adjusted correctly. The state of Indiana has taken non-standard action. The time investment needed to adjust calendars in response is a one-time resource hit, but will be worthwhile if you depend on Exchange calendaring.

At IU, UITS has developed a web-based tool to ease the task of checking and adjusting calendar items for IU Exchange users. For more information, see the Knowledge Base document ARCHIVED: At IU, how do I use the Time Zone Checker to update my Exchange calendar?

The Knowledge Base document ARCHIVED: How does Indiana's adoption of Daylight Saving Time affect my Exchange calendar? describes an alternative method for streamlining the manual process of adjusting calendar items. This document helps users categorize their calendar items so they can more easily identify those that might need to be changed. The document describes how to use the built-in Outlook Advanced Find tool to search for certain types of calendar items, review the search results, and modify each item as needed. The document details the necessary steps for each type of item.

Note: You can save Outlook Advanced Find searches and share them with others, saving others from having to build the same searches from scratch.

Other solutions

Export and import

An obvious solution is to export all calendar items from your mailbox, change your system time zone setting, and then import the items back into your mailbox. The items will then appear to be correct on your calendar.

This solution is appropriate, if selectively applied. It is best used for Exchange Public Folder calendars and tasks. Be sure to use Outlook to export items to a Personal Folder file (.pst), rather than a Comma Separated Values (.csv) file.

Keep the following points in mind:

  • If you use a CSV file as an export destination, you will lose any attachments to exported items, and recurring series will be broken into multiple single instances; there may be additional negative consequences.
  • Regardless of file format, this method does not take into account who the meeting organizer is, and the meeting organizer should send updates to other attendees and resources. Meeting attendees should not update the appointment, but wait for (or prompt) the meeting organizer to send an update. Otherwise they could make changes of which the meeting organizer, other attendees, and resources are not aware.
  • If you use this method, there's no way to send updates to other attendees or resources.
  • There is no regard for the original time zone setting of the appointment, which could be something other than Indiana (East) or Eastern if it was organized by someone in another time zone.
  • Use the available filter option to export only appointments that do not have other attendees and resources. This will help selectively apply this method. Although this will help move appointments to the proper calendar time, the time zone data (TZID) does not get updated on the Exchange server, which could result in the appointment or meeting being off by an hour.

Script a solution

Microsoft has been clear on one point: it will not support any automated solutions for updating Exchange calendar entries to adjust for time zone change. Too many variables require some measure of human intervention. Microsoft knowledge base article 915577 says:

"Because many meetings currently occur across time zones, any automatic solution that Microsoft might provide would still require a manual adjustment of some meeting times to resolve Free/Busy conflicts and Resource conflicts."

Stay on Indiana (East) and manually move your clock to adjust for DST

While this might seem like a good idea, it wouldn't work unless you were isolated and interacted only with others who are on Indiana (East) too. In theory, you do have the option of not adjusting your computer to the new time zone. This will work as long as you remember to set your clock ahead and back twice a year and mentally adjust your appointments and meeting requests. Those items sent to you will be adjusted automatically based on your Windows settings and appear on your calendar to be correct. However, you could end up hour off from when the appointment or meeting request was scheduled.

Also note that Microsoft (and other software vendors) will abandon support for any special time zones for Indiana. Microsoft's knowledge base article 914837 says:

"Microsoft Windows users in Indiana will have to change their Windows time zone settings from Indiana (East) to either Eastern Time (US & Canada) or Central Time (US & Canada). The Indiana (East) time zone setting will become obsolete and should not be used in the future. Indiana residents should use local sources of information to determine the correct time zone."

Following are some major drawbacks to this approach:

  • It provides only the illusion of a fix, merely causing an individual calendar to appear accurate while disregarding the rest of the world. It simply fixes "clock time", which is no solution at all.
  • Any new calendar entries will be stamped with the Indiana (East) time zone setting, thus perpetuating and increasing the problem.
  • This would only work in isolation, meaning all other meeting attendees and resources must be on Indiana (East) as well.
  • This creates a problem for people using other time zone settings, including Eastern, who interact with the people who remain on Indiana (East).
  • One or more of the computers or servers could be time-synchronized with a server not configured to support this time configuration.


There is no quick-fix solution. Due to the complex and personal nature of calendars, some level of human interaction has to be included in this process. The power of computing can be used to help facilitate the search and identify process, but the owner and/or delegate must be involved to confirm actions.

Keep in mind that changing time zones is not trivial. Very real conflicts will arise that require adjustments. During DST periods, Indiana will now be one hour ahead of "Indiana time" as it has been known for the past thirty-six years, relative to all other time zones.

This is document atrm in the Knowledge Base.
Last modified on 2021-09-07 17:07:16.