Time Change Information - Funduc Software

Funduc Software

Daylight Savings, Standard Time & Reported File Times

User's of our Directory Toolkit sometimes observe that when a "Daylight Savings" or "Standard Time" changeover occurs, path comparisons between two computers suddenly show a difference in file times even though no changes were made to the files in either path.

This is probably because of one or more of the following:
- One or both computers is an NT class computer such as Windows NT/2000/XP (Home or Pro)
- The two computers physically reside in different time zones
- Time Zone & "Daylight Savings" rules differ between the two computers

This happens because Windows NT/2000/XP automatically adjusts the file time reported by the operating system based on Daylight Savings rules and Time Zone in effect on the computer running Directory Toolkit. Directory Toolkit collects the file date/time information it reports from the operating system itself. If the operating system returns an "adjusted" time to Directory Toolkit, then Directory Toolkit ends up reporting an adjusted file time.

This behavior can be very puzzling. The table below depicts the effect of the automatic Windows NT/2000/XP "Daylight Savings Adjustment" on file times reported for a test file created 03/37/2000, 03:00am (USA Eastern) under US English Windows 98. The file was copied to a Windows 2000 machine (FAT32 partition), a Directory Toolkit comparison of the two paths was opened, and the computer dates were changed on the two computers as per the conditions below. The NT 2000 machine was configured to "Automatically Adjust for Daylight Savings". Directory Toolkit was not set to perform "Binary File Comparisons" and no adjustments were made to the default "Time Check Precision" setting under Options-Compare (see below).


Reported File Time Stamp and Daylight Savings Compensation
	MS-DOS		Explorer		Directory Toolkit
Condition	Win98	Win2000	Win98	Win2000	Win98	Win2000
1	3:00am	3:00am	3:00am	3:00am	3:00am	3:00am
2	3:00am	3:00am	3:00am	4:00am	3:00am	4:00am
3	3:00am	3:00am	3:00am	3:00am	3:00am	3:00am
4	3:00am	3:00am	3:00am	2:00am	3:00am	2:00am

Condition - Date settings for the 2 machines
#1 - Win98 Machine = 03/27 , Win2000 Machine = 03/27 #2 - Win98 Machine = 06/27 , Win2000 Machine = 03/27 #3 - Win98 Machine = 06/27 , Win2000 Machine = 06/27 #4 - Win98 Machine = 03/27 , Win2000 Machine = 06/27

Note that the differences in the reported file times above. Windows 98 does not make Daylight Savings compensations in the reported file times, hence the file times reported by that machine for files that reside on that machine never change. It is also interesting to note that the MS-DOS time stamp under Windows 2000 does not change even though the OS reports a different time to Explorer and Directory Toolkit.

A search of the Microsoft Knowledge Base (support.microsoft.com) using the keywords "Time Zone" or "Daylight Savings" will turn up a variety of articles on this general issue. A good overall description is: Time Stamp Changes with Daylight Savings (Article Q129574).

We point out that although the above article refers to NTFS, the above test shows that this also happens under Windows 2000 on a FAT32 partition.

There are several ways to deal with this.

1) Make sure all your machines are set to the correct time zone for their location. Allow them to adjust themselves for daylight savings or not. Don't fiddle with the time zone rules for your computer. Or any of the computers in your network. Although NT's behavior of adjusting the reported file times may be unnerving to purists, our support experience is that weird situations are most likely to arise when someone has tinkered with the default Windows OS settings or a machine simply is set to the wrong time zone.

2) Change the Directory Toolkit "Time Check Precision" setting (Options-Compare) from the default of 3 second to a value covering the new time differences between the two machines. For example, assuming the file content (and hence file size) has not changed, a value of 3600 would cause Directory Toolkit to report the files as the same even though their time stamp is one hour apart. The risks of this method are that "Time Check Precision" is a +/- range and not a specific value. Files 3 min, 15 min, 45 min would also be reported as the same. You may not want this...

3) Turn on the Directory Toolkit Binary Comparison mode, which will now report the files as the same.

4) Use the Directory Toolkit "Add To File Time" setting in the Touch dialog to quickly touch the files on one or the other path. This field adds (or subtracts) the number of seconds you specify from the current file time. For example, to add one hour to the current file time, enter a value of 3600.

5) Disable "Automatically Adjust for Daylight Savings" under Time Setting for Windows 2000, which appears to disable the Daylight Savings Compensation. This has not been tested yet under NT 4.0. Note that this will also prevent your computer from automatically detecting when a Daylight Savings date event has transpired.

6) Use our freeware TZAdjust utility, which permits to you to adjust the Time Zone rules for your computer including the compensation value to use.

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