fix gmtime; closes #1366

2 files changed, 57 insertions, 4 deletions

diff --git a/src/library.js b/src/library.js
index b45ef8db..6613335b 100644
--- a/src/library.js
+++ b/src/library.js
@@ -6144,9 +6144,14 @@ LibraryManager.library = {
     {{{ makeSetValue('tmPtr', 'offsets.tm_wday', 'date.getUTCDay()', 'i32') }}}
     {{{ makeSetValue('tmPtr', 'offsets.tm_gmtoff', '0', 'i32') }}}
     {{{ makeSetValue('tmPtr', 'offsets.tm_isdst', '0', 'i32') }}}
-
-    var start = new Date(date.getFullYear(), 0, 1);
-    var yday = Math.round((date.getTime() - start.getTime()) / (1000 * 60 * 60 * 24));
+    var start = new Date(date); // define date using UTC, start from Jan 01 00:00:00 UTC
+    start.setUTCDate(1);
+    start.setUTCMonth(0);
+    start.setUTCHours(0);
+    start.setUTCMinutes(0);
+    start.setUTCSeconds(0);
+    start.setUTCMilliseconds(0);
+    var yday = Math.floor((date.getTime() - start.getTime()) / (1000 * 60 * 60 * 24));
     {{{ makeSetValue('tmPtr', 'offsets.tm_yday', 'yday', 'i32') }}}
 
     var timezone = "GMT";
@@ -6157,7 +6162,6 @@ LibraryManager.library = {
 
     return tmPtr;
   },
-
   timegm__deps: ['mktime'],
   timegm: function(tmPtr) {
     _tzset();
diff --git a/tests/runner.py b/tests/runner.py
index 976772ce..0261c85a 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -5025,6 +5025,55 @@ The current type of b is: 9
       '''
       self.do_run(src, 'time: ') # compilation check, mainly
 
+    def test_gmtime(self):
+      src = r'''
+        #include <stdio.h>
+        #include <stdlib.h>
+        #include <time.h>
+
+        int main(void)
+        {
+            time_t t=time(NULL);
+            struct tm *ptm=gmtime(&t);
+            struct tm tmCurrent=*ptm;
+            int hour=tmCurrent.tm_hour;
+
+            t-=hour*3600; // back to midnight
+            for(hour=0;hour<24;hour++)
+            {
+                ptm=gmtime(&t);
+                // tm_yday must be constant all day...
+                printf("yday: %d, hour: %d\n", ptm->tm_yday, hour);
+                t+=3600; // add one hour
+            }
+            return(0);
+        }
+      '''
+      self.do_run(src, '''yday: 210, hour: 0
+yday: 210, hour: 1
+yday: 210, hour: 2
+yday: 210, hour: 3
+yday: 210, hour: 4
+yday: 210, hour: 5
+yday: 210, hour: 6
+yday: 210, hour: 7
+yday: 210, hour: 8
+yday: 210, hour: 9
+yday: 210, hour: 10
+yday: 210, hour: 11
+yday: 210, hour: 12
+yday: 210, hour: 13
+yday: 210, hour: 14
+yday: 210, hour: 15
+yday: 210, hour: 16
+yday: 210, hour: 17
+yday: 210, hour: 18
+yday: 210, hour: 19
+yday: 210, hour: 20
+yday: 210, hour: 21
+yday: 210, hour: 22
+yday: 210, hour: 23
+''')
 
     def test_strptime_tm(self):
       src=r'''