Implement some rudimentary time-zone code so that we can produce

reasonably accurate time zones in RFC-822 dates.

diff --git a/v7/src/runtime/datime.scm b/v7/src/runtime/datime.scm
index 6b6b54da3bdc50b6daecc334ee8718ece1df42b7..d68c96c3a26eebb0893438f47ebff596b81ca99a 100644 (file)
--- a/v7/src/runtime/datime.scm
+++ b/v7/src/runtime/datime.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: datime.scm,v 14.7 1995/04/15 06:56:27 cph Exp $
+$Id: datime.scm,v 14.8 1995/04/22 23:37:09 cph Exp $
 
 Copyright (c) 1988-95 Massachusetts Institute of Technology
 
@@ -138,4 +138,35 @@ MIT in each case. |#
                   (if (< second 10) ":0" ":")
                   (number->string second)
                   " "
-                  (if (< hour 12) "AM" "PM"))))
\ No newline at end of file
+                  (if (< hour 12) "AM" "PM"))))
+
+(define (time-zone? object)
+  (and (number? object)
+       (exact? object)
+       (<= -24 object 24)
+       (integer? (* 3600 object))))
+
+(define (time-zone->string tz)
+  (if (not (time-zone? tz))
+      (error:wrong-type-argument tz "time zone" 'TIME-ZONE->STRING))
+  (let ((minutes (round (* 60 (- tz)))))
+    (let ((qr (integer-divide (abs minutes) 60)))
+      (string-append (if (< minutes 0) "-" "+")
+                    (string-pad-left (integer-divide-quotient qr) 2 #\0)
+                    (string-pad-left (integer-divide-remainder qr) 2 #\0)))))
+
+(define (decoded-time/daylight-savings-time? dt)
+  ;; In current implementation, DAY-OF-WEEK field might be missing, so
+  ;; there this will return wrong answer near the changeovers.
+  (let ((month (decoded-time/month dt)))
+    (cond ((= 4 month)
+          (or (> (decoded-time/day dt) 7)
+              (not (eqv? (decoded-time/day-of-week dt) 6))
+              (> (decode-time/hour dt) 1)))
+         ((= 10 month)
+          (or (< (decoded-time/day dt) 25)
+              (not (eqv? (decoded-time/day-of-week dt) 6))
+              ;; Since DT is a local time, it's impossible to
+              ;; tell whether we're in the overlapped hour.
+              (< (decode-time/hour dt) 3)))
+         (else (<= 5 month 9)))))
\ No newline at end of file

diff --git a/v7/src/runtime/runtime.pkg b/v7/src/runtime/runtime.pkg
index 568a3b353f9c80d3ee0f6613fcbfaac2bb029e3d..fda3995f5a37c959c7ea6d83874ed22809c043b0 100644 (file)
--- a/v7/src/runtime/runtime.pkg
+++ b/v7/src/runtime/runtime.pkg
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: runtime.pkg,v 14.252 1995/04/15 06:10:04 cph Exp $
+$Id: runtime.pkg,v 14.253 1995/04/22 23:37:23 cph Exp $
 
 Copyright (c) 1988-95 Massachusetts Institute of Technology
 
@@ -375,6 +375,7 @@ MIT in each case. |#
          decoded-time/date-string
          decoded-time/day
          decoded-time/day-of-week
+         decoded-time/daylight-savings-time?
          decoded-time/hour
          decoded-time/minute
          decoded-time/month
@@ -387,7 +388,9 @@ MIT in each case. |#
          make-decoded-time
          month/long-string
          month/max-days
-         month/short-string))
+         month/short-string
+         time-zone->string
+         time-zone?))
 
 (define-package (runtime debugger)
   (files "debug")