Possible TZ Data Errors with every 1st / 2nd / 3rd Xday of the month

Andy Lipscomb AndyLipscomb at decosimo.com
Wed May 31 12:13:14 UTC 2006

No, in that case at least, the data is correct. The second Saturday of a month can be between the 8th and the 14th, inclusive; this year, the second Saturday of October is the 14th. Since the changeover occurs at 24:00 on that Saturday and Unix doesn't like 24:00, it is coded as 0:00 the following day, which is the 15th this year, and in general can run from the 9th to the 15th. Thus, Sun>=9 is correct. (This is not the "second Sunday," but the "Sunday after the second Saturday." USA readers will see the resemblance to Election Day.)


From: Dr Hingston [mailto:dr.hingston at paradise.net.nz] 
Sent: Wed 31 May 2006 04:31
To: tz at lecserver.nci.nih.gov
Subject: Possible TZ Data Errors with every 1st / 2nd / 3rd Xday of the month

Dear List  Members

Woops, seems I got the address wrong, my apologies!  I hope this is better!


Rule Chile 1999 max - Oct Sun>=9 4:00u 1:00 S
Rule Chile 2000 max - Mar Sun>=9 3:00u 0 -

The expression Sun>=9 from the above rules would appear to me to be incorrect, as it suggests the third Sunday in some years.   e.g. October this year.

Summary:  Supreme Decree Number 1,489 (6 October 1970) - This law, enacted during the presidency of Eduardo Frei Montalva, declared that Daylight Saving Time will advance clocks by one hour, beginning the second Saturday of October, and ending the second Saturday of March. Chilean time is administered by the Chilean Navy's Hydrographic and Oceanographic Service (SHOA).

On discussion with the Chilean Consulate the above is confirmed, and time for changeover is midnight Saturday (I take to mean 00:00 Sunday)

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