Fixed timezone handling

* mktime always interprets its input as local time even on systems where
   gmtoff is present, so using it is utterly useless for anything but getting
   the local timezone. Removed all other usage of gmtoff to avoid confusion.
 * Properly handle timezone offset in toTime()
 * Properly handle timezone offset in `$` because asctime also interprets its
   input as local time
 * Also tried to fix the JavaScript implementation

lib/pure/times.nim

@@ -184,7 +184,8 @@ proc getGMTime*(t: Time): TimeInfo {.tags: [TimeEffect], raises: [], benign.}
   ## converts the calendar time `t` to broken-down time representation,
   ## expressed in Coordinated Universal Time (UTC).
 
-proc timeInfoToTime*(timeInfo: TimeInfo): Time {.tags: [], benign, deprecated.}
+proc timeInfoToTime*(timeInfo: TimeInfo): Time
+    {.tags: [TimeEffect], benign, deprecated.}
   ## converts a broken-down time structure to
   ## calendar time representation. The function ignores the specified
   ## contents of the structure members `weekday` and `yearday` and recomputes
@@ -193,7 +194,7 @@ proc timeInfoToTime*(timeInfo: TimeInfo): Time {.tags: [], benign, deprecated.}
   ## **Warning:** This procedure is deprecated since version 0.14.0.
   ## Use ``toTime`` instead.
 
-proc toTime*(timeInfo: TimeInfo): Time {.tags: [], benign.}
+proc toTime*(timeInfo: TimeInfo): Time {.tags: [TimeEffect], benign.}
   ## converts a broken-down time structure to
   ## calendar time representation. The function ignores the specified
   ## contents of the structure members `weekday` and `yearday` and recomputes
@@ -211,7 +212,8 @@ proc fromSeconds*(since1970: int64): Time {.tags: [], raises: [], benign.} =
 proc toSeconds*(time: Time): float {.tags: [], raises: [], benign.}
   ## Returns the time in seconds since the unix epoch.
 
-proc `$` *(timeInfo: TimeInfo): string {.tags: [], raises: [], benign.}
+proc `$` *(timeInfo: TimeInfo): string
+    {.tags: [TimeEffect], raises: [], benign.}
   ## converts a `TimeInfo` object to a string representation.
 proc `$` *(time: Time): string {.tags: [], raises: [], benign.}
   ## converts a calendar time to a string representation.
@@ -424,7 +426,8 @@ when not defined(JS):
 
 when not defined(JS):
   # C wrapper:
-  when defined(freebsd) or defined(netbsd) or defined(openbsd):
+  when defined(freebsd) or defined(netbsd) or defined(openbsd) or
+      defined(macosx):
     type
       StructTM {.importc: "struct tm", final.} = object
         second {.importc: "tm_sec".},
@@ -479,46 +482,24 @@ when not defined(JS):
     const
       weekDays: array[0..6, WeekDay] = [
         dSun, dMon, dTue, dWed, dThu, dFri, dSat]
-    when defined(freebsd) or defined(netbsd) or defined(openbsd):
-      TimeInfo(second: int(tm.second),
-        minute: int(tm.minute),
-        hour: int(tm.hour),
-        monthday: int(tm.monthday),
-        month: Month(tm.month),
-        year: tm.year + 1900'i32,
-        weekday: weekDays[int(tm.weekday)],
-        yearday: int(tm.yearday),
-        isDST: tm.isdst > 0,
-        tzname: if local:
-            if tm.isdst > 0:
-              getTzname().DST
-            else:
-              getTzname().nonDST
+    TimeInfo(second: int(tm.second),
+      minute: int(tm.minute),
+      hour: int(tm.hour),
+      monthday: int(tm.monthday),
+      month: Month(tm.month),
+      year: tm.year + 1900'i32,
+      weekday: weekDays[int(tm.weekday)],
+      yearday: int(tm.yearday),
+      isDST: tm.isdst > 0,
+      tzname: if local:
+          if tm.isdst > 0:
+            getTzname().DST
           else:
-            "UTC",
-        # BSD stores in `gmtoff` offset east of UTC in seconds,
-        # but posix systems using west of UTC in seconds
-        timezone: if local: -(tm.gmtoff) else: 0
-      )
-    else:
-      TimeInfo(second: int(tm.second),
-        minute: int(tm.minute),
-        hour: int(tm.hour),
-        monthday: int(tm.monthday),
-        month: Month(tm.month),
-        year: tm.year + 1900'i32,
-        weekday: weekDays[int(tm.weekday)],
-        yearday: int(tm.yearday),
-        isDST: tm.isdst > 0,
-        tzname: if local:
-            if tm.isdst > 0:
-              getTzname().DST
-            else:
-              getTzname().nonDST
-          else:
-            "UTC",
-        timezone: if local: getTimezone() else: 0
-      )
+            getTzname().nonDST
+        else:
+          "UTC",
+      timezone: if local: getTimezone() else: 0
+    )
 
 
   proc timeInfoToTM(t: TimeInfo): StructTM =
@@ -569,12 +550,18 @@ when not defined(JS):
   proc timeInfoToTime(timeInfo: TimeInfo): Time =
     var cTimeInfo = timeInfo # for C++ we have to make a copy,
     # because the header of mktime is broken in my version of libc
-    return mktime(timeInfoToTM(cTimeInfo))
+    result = mktime(timeInfoToTM(cTimeInfo))
+    # mktime is defined to interpret the input as local time. As timeInfoToTM
+    # does ignore the timezone, we need to adjust this here.
+    result = Time(TimeImpl(result) - getTimezone() + timeInfo.timezone)
 
   proc toTime(timeInfo: TimeInfo): Time =
     var cTimeInfo = timeInfo # for C++ we have to make a copy,
     # because the header of mktime is broken in my version of libc
-    return mktime(timeInfoToTM(cTimeInfo))
+    result = mktime(timeInfoToTM(cTimeInfo))
+    # mktime is defined to interpret the input as local time. As timeInfoToTM
+    # does ignore the timezone, we need to adjust this here.
+    result = Time(TimeImpl(result) - getTimezone() + timeInfo.timezone)
 
   proc toStringTillNL(p: cstring): string =
     result = ""
@@ -584,8 +571,13 @@ when not defined(JS):
       inc(i)
 
   proc `$`(timeInfo: TimeInfo): string =
+    # asctime interprets its input as local time, so we first convert the value
+    # to local time if necessary
+    let
+      localTimeInfo = if timeInfo.timezone == getTimezone(): timeInfo else:
+        getLocalTime(toTime(timeInfo))
+      p = asctime(timeInfoToTM(localTimeInfo))
     # BUGFIX: asctime returns a newline at the end!
-    var p = asctime(timeInfoToTM(timeInfo))
     result = toStringTillNL(p)
 
   proc `$`(time: Time): string =
@@ -675,14 +667,7 @@ elif defined(JS):
     result.weekday = weekDays[t.getUTCDay()]
     result.yearday = 0
 
-  proc timeInfoToTime*(timeInfo: TimeInfo): Time =
-    result = internGetTime()
-    result.setSeconds(timeInfo.second)
-    result.setMinutes(timeInfo.minute)
-    result.setHours(timeInfo.hour)
-    result.setMonth(ord(timeInfo.month))
-    result.setFullYear(timeInfo.year)
-    result.setDate(timeInfo.monthday)
+  proc timeInfoToTime*(timeInfo: TimeInfo): Time = toTime(timeInfo)
 
   proc toTime*(timeInfo: TimeInfo): Time =
     result = internGetTime()
@@ -692,6 +677,7 @@ elif defined(JS):
     result.setMonth(ord(timeInfo.month))
     result.setFullYear(timeInfo.year)
     result.setDate(timeInfo.monthday)
+    result = result + initInterval(seconds=timeInfo.timezone)
 
   proc `$`(timeInfo: TimeInfo): string = return $(toTime(timeInfo))
   proc `$`(time: Time): string = return $time.toLocaleString()
@@ -1257,7 +1243,7 @@ proc parse*(value, layout: string): TimeInfo =
   let correctDST = getLocalTime(toTime(info))
   info.isDST = correctDST.isDST
 
-  # Now we preocess it again with the correct isDST to correct things like
+  # Now we process it again with the correct isDST to correct things like
   # weekday and yearday.
   return getLocalTime(toTime(info))