How Outlook handles time zones for meeting requests

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This article was previously published under Q195900

SUMMARY

This article discusses how Microsoft Outlook schedules meeting requests over multiple time zones.

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MORE INFORMATION

Three factors affect the scheduling of a meeting in Outlook:

The computer's clock setting (time).
The computer's local time zone setting, which consists of an offset value to Greenwich mean time (GMT).
The computer's daylight-saving time adjustment setting.

All three factors must be correct on both the meeting requestor's computer and on each attendee's computer. Otherwise, Outlook cannot schedule the meeting time correctly.

Outlook time stamps the message request with the Greenwich mean time for the meeting. Outlook calculates Greenwich mean time by using the computer's clock time, plus or minus the local time zone adjustment, minus (depending upon the time of year) the daylight-saving time adjustment.

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Example

Assume someone in the central standard time zone during the summer months (when daylight-saving time is in effect), wishes to schedule a meeting at 3:00 P.M. (their local time), with a user in the Pacific time zone.

The central standard time zone (CST) has a Greenwich mean time offset of -6:00 hours and a daylight-saving time (DST) adjustment of +1:00 hour.

Outlook calculates the time for the meeting in Greenwich mean time, as follows:

   Local time for the meeting:      3:00 P.M. central standard time
   Adjustment for CST offset:      +6:00 hours
   Remove DST adjustment:          -1:00 hour
                                   -----
   Resulting Greenwich mean time:   8:00 P.M. Greenwich mean time

When the attendee receives the meeting request, Outlook calculates the current local time by using the message's Greenwich mean time stamp, plus or minus the local time zone adjustment, plus (depending upon the time of year) the daylight-saving time adjustment. Outlook uses this time to schedule the meeting for the recipient.

Continuing the Example:

The Pacific standard time zone (PST) has a Greenwich mean time offset of - 8:00 hours and a daylight-saving time (DST) adjustment of +1:00 hour.

Outlook calculates the time for the meeting in Pacific standard time, as follows:

   Meeting time in GMT:             8:00 P.M. Greenwich mean time
   Adjustment for PST offset:      -8:00 hours
   Add DST adjustment:             +1:00 hour
                                   -----
   Local time for the meeting:      1:00 P.M. Pacific standard time

NOTE: As soon as Outlook receives the meeting request it calculates the meeting time for the recipient and schedules it on the calendar. If any of the three factors listed earlier in this article are incorrect at that time, the meeting time will be incorrect. You cannot correct the time after the fact by correcting the factor in error; you must open the meeting request and manually correct the scheduled time.

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