Clarify exactly when DST-changeover-induced regression test failures

can be expected to occur.

diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 8c0df408783eefd9a4ae8d61fdd5f1a6ee5d031b..a5dac7a14112b7495e43537964ece1bc4f7d7ce6 100644 (file)
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -1,4 +1,4 @@
-
+
 
  
   Regression Tests
@@ -201,14 +201,26 @@ gmake installcheck
     Date and time differences
 
     
-     Some of the queries in the horology test will
+     A few of the queries in the horology test will
      fail if you run the test on the day of a daylight-saving time
-     changeover, or the day before or after one.  These queries assume
-     that the intervals between midnight yesterday, midnight today and
+     changeover, or the day after one.  These queries expect that
+     the intervals between midnight yesterday, midnight today and
      midnight tomorrow are exactly twenty-four hours --- which is wrong
      if daylight-saving time went into or out of effect meanwhile.
     
 
+    
+     
+      Because USA daylight-saving rules are used, this problem always
+      occurs on the first Sunday of April, the last Sunday of October,
+      and their following Mondays, regardless of when daylight-saving
+      is in effect where you live.  Also note that the problem appears or
+      disappears at midnight Pacific time (UTC-7 or UTC-8), not midnight
+      your local time.  Thus the failure may appear late on Saturday or
+      persist through much of Tuesday, depending on where you live.
+     
+    
+
     
      Most of the date and time results are dependent on the time zone
      environment.  The reference files are generated for time zone