Calc: fix formatting and parsing Unix time (bug#43759)

The number of days from epoch to Jan 1, 1970 that was used in parsing
and formatting Unix time was incorrect.  The previous fix
(in e368697ce36) was incomplete.

Reported by Vincent Belaïche.

* lisp/calc/calc-forms.el (math-unix-epoch): New constant.
(math-format-date-part, math-parse-standard-date, calcFunc-unixtime):
Use math-unix-epoch instead of a constant that is sometimes wrong.
* test/lisp/calc/calc-tests.el (calc-unix-date): New test.

diff --git a/lisp/calc/calc-forms.el b/lisp/calc/calc-forms.el
index 6d70126c098f863bdedf77f6ccbabccba09ae6b4..a2f66968665fb023fe5c23c62a7350aaec28355f 100644 (file)
--- a/lisp/calc/calc-forms.el
+++ b/lisp/calc/calc-forms.el
@@ -709,6 +709,10 @@ as measured in the number of days before December 31, 1 BC (Gregorian).")
   "The beginning of the Julian date calendar,
 as measured in the integer number of days before December 31, 1 BC (Gregorian).")
 
+(defconst math-unix-epoch 719163
+  "The beginning of Unix time: days from December 31, 1 BC (Gregorian)
+to Jan 1, 1970 AD.")
+
 (defun math-format-date-part (x)
   (cond ((stringp x)
         x)
@@ -730,7 +734,8 @@ as measured in the integer number of days before December 31, 1 BC (Gregorian)."
                               (math-floor math-fd-date)
                               math-julian-date-beginning-int)))
        ((eq x 'U)
-        (math-format-number (nth 1 (math-date-parts math-fd-date 719164))))
+        (math-format-number (nth 1 (math-date-parts math-fd-date
+                                                     math-unix-epoch))))
         ((memq x '(IYYY Iww w))
          (progn
            (or math-fd-iso-dt
@@ -1173,7 +1178,7 @@ as measured in the integer number of days before December 31, 1 BC (Gregorian)."
                      (setq num (math-match-substring math-pd-str 0)
                            math-pd-str (substring math-pd-str (match-end 0))
                            num (math-date-to-dt
-                                (math-add 719164
+                                (math-add math-unix-epoch
                                           (math-div (math-read-number num)
                                                     '(float 864 2))))
                            hour (nth 3 num)
@@ -1434,11 +1439,11 @@ as measured in the integer number of days before December 31, 1 BC (Gregorian)."
 (defun calcFunc-unixtime (date &optional zone)
   (if (math-realp date)
       (progn
-       (setq date (math-add 719163 (math-div date '(float 864 2))))
+       (setq date (math-add math-unix-epoch (math-div date '(float 864 2))))
        (list 'date (math-sub date (math-div (calcFunc-tzone zone date)
                                             '(float 864 2)))))
     (if (eq (car date) 'date)
-       (math-add (nth 1 (math-date-parts (nth 1 date) 719163))
+       (math-add (nth 1 (math-date-parts (nth 1 date) math-unix-epoch))
                  (calcFunc-tzone zone date))
       (math-reject-arg date 'datep))))
 

diff --git a/test/lisp/calc/calc-tests.el b/test/lisp/calc/calc-tests.el
index 4dded007f7971659773994da0729384ed46f945f..0df96a0e2dbba2ef90a065057b2c307dadbba495 100644 (file)
--- a/test/lisp/calc/calc-tests.el
+++ b/test/lisp/calc/calc-tests.el
@@ -534,6 +534,46 @@ An existing calc stack is reused, otherwise a new one is created."
       )
   ))
 
+(ert-deftest calc-unix-date ()
+  (let* ((d-1970-01-01 (math-parse-date "1970-01-01"))
+         (d-2020-09-07 (math-parse-date "2020-09-07"))
+         (d-1991-01-09-0600 (math-parse-date "1991-01-09 06:00")))
+    ;; calcFunc-unixtime (command "t U") converts a date value to Unix time,
+    ;; and a number to a date.
+    (should (equal d-1970-01-01 '(date 719163)))
+    (should (equal (calcFunc-unixtime d-1970-01-01 0) 0))
+    (should (equal (calc-tests--calc-to-number (cadr (calcFunc-unixtime 0 0)))
+                   (cadr d-1970-01-01)))
+    (should (equal (calcFunc-unixtime d-2020-09-07 0)
+                   (* (- (cadr d-2020-09-07)
+                         (cadr d-1970-01-01))
+                      86400)))
+    (should (equal (calcFunc-unixtime d-1991-01-09-0600 0)
+                   663400800))
+    (should (equal (calc-tests--calc-to-number
+                    (cadr (calcFunc-unixtime 663400800 0)))
+                   726841.25))
+
+    (let ((calc-date-format '(U)))
+      ;; Test parsing Unix time.
+      (should (equal (calc-tests--calc-to-number
+                      (cadr (math-parse-date "0")))
+                     719163))
+      (should (equal (calc-tests--calc-to-number
+                      (cadr (math-parse-date "469324800")))
+                     (+ 719163 (/ 469324800 86400))))
+      (should (equal (calc-tests--calc-to-number
+                      (cadr (math-parse-date "663400800")))
+                     726841.25))
+
+      ;; Test formatting Unix time.
+      (should (equal (math-format-date d-1970-01-01) "0"))
+      (should (equal (math-format-date d-2020-09-07)
+                     (number-to-string (* (- (cadr d-2020-09-07)
+                                             (cadr d-1970-01-01))
+                                          86400))))
+      (should (equal (math-format-date d-1991-01-09-0600) "663400800")))))
+
 (provide 'calc-tests)
 ;;; calc-tests.el ends here