English

FAQ: How does daylight savings time affect ArcGIS and ArcIMS on Sun and Linux Systems?

Question

How does daylight savings time affect ArcGIS and ArcIMS on Sun and Linux Systems?

Answer

Background

On March 11, 2007, the start and end dates for daylight savings time (DST) in the United States changed to comply with the Energy Policy Act of 2005. Daylight savings time begins the second Sunday of March and ends the first Sunday of November. Due to this change, operating system and application software updates may be required to ensure that the system time is accurate.

How this affects ArcGIS and ArcIMS ArcMap Server

Two system calls, used by ArcGIS and ArcIMS ArcMap Server on Solaris and Linux, base their time calculations on the assumption that DST is in effect between April 2nd and Oct 29th. If the local Solaris/Linux system administrator updates the system with the new DST schedule of this year, there is a 1 hour difference between the time as reported by above functions and the actual local time. This difference exists for the two weeks between March 11th and April 2nd and then for the two weeks between October 29th and November 4th. These issues affect the following areas of ArcGIS and ArcIMS ArcMap Server:

· Tracking and Tracking Server
· Localized time values across time zones
· Network
· Travel time estimates when the path crosses time zone boundaries
· Displayed and stored date/time values
· PNG, SVG, and schematics diagram data files

In the area listed above, the determined time is off by one hour. For example, at 7:00AM with the new DST, the software reports the time as 8:00AM. We believe the impact of this to be minimal; however, any issues resolve themselves once the original DST date arrives. On November 4, 2007, when the time changes again back to Standard Time, we expect to have a patch available for those few areas of the software that are affected.

If your workflow uses the affected parts of ArcGIS or ArcIMS ArcMap Server on Solaris or Linux as described above and cannot tolerate being off by an hour for the affected two weeks, please contact Esri Support Services.

Related Information