tree-wide: fix how we set $TZ

According to tzset(3) we need to prefix timezone names with ":". Let's
do so hence, to avoid any ambiguities and follow documented behaviour.

man/systemd.time.xml

@@ -136,9 +136,8 @@
     evaluated relative to the UNIX time epoch 1st Jan, 1970,
     00:00.</para>
 
-    <para>Examples for valid timestamps and their normalized form
-    (assuming the current time was 2012-11-23 18:15:22 and the timezone
-    was UTC+8, for example TZ=Asia/Shanghai):</para>
+    <para>Examples for valid timestamps and their normalized form (assuming the current time was 2012-11-23
+    18:15:22 and the timezone was UTC+8, for example <literal>TZ=:Asia/Shanghai</literal>):</para>
 
     <programlisting>  Fri 2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13
       2012-11-23 11:12:13 → Fri 2012-11-23 11:12:13

src/basic/time-util.c

@@ -832,8 +832,12 @@ int parse_timestamp(const char *t, usec_t *usec) {
         }
         if (r == 0) {
                 bool with_tz = true;
+                char *colon_tz;
 
-                if (setenv("TZ", tz, 1) != 0) {
+                /* tzset(3) says $TZ should be prefixed with ":" if we reference timezone files */
+                colon_tz = strjoina(":", tz);
+
+                if (setenv("TZ", colon_tz, 1) != 0) {
                         shared->return_value = negative_errno();
                         _exit(EXIT_FAILURE);
                 }

src/shared/calendarspec.c

@@ -1352,7 +1352,12 @@ int calendar_spec_next_usec(const CalendarSpec *spec, usec_t usec, usec_t *ret_n
                 return r;
         }
         if (r == 0) {
-                if (setenv("TZ", spec->timezone, 1) != 0) {
+                char *colon_tz;
+
+                /* tzset(3) says $TZ should be prefixed with ":" if we reference timezone files */
+                colon_tz = strjoina(":", spec->timezone);
+
+                if (setenv("TZ", colon_tz, 1) != 0) {
                         shared->return_value = negative_errno();
                         _exit(EXIT_FAILURE);
                 }

src/test/test-calendarspec.c

@@ -43,9 +43,12 @@ static void test_next(const char *input, const char *new_tz, usec_t after, usec_
         if (old_tz)
                 old_tz = strdupa(old_tz);
 
-        if (new_tz)
-                assert_se(setenv("TZ", new_tz, 1) >= 0);
-        else
+        if (new_tz) {
+                char *colon_tz;
+
+                colon_tz = strjoina(":", new_tz);
+                assert_se(setenv("TZ", colon_tz, 1) >= 0);
+        } else
                 assert_se(unsetenv("TZ") >= 0);
         tzset();
 

src/test/test-time-util.c

@@ -475,7 +475,7 @@ static void test_in_utc_timezone(void) {
         assert_se(timezone == 0);
         assert_se(daylight == 0);
 
-        assert_se(setenv("TZ", "Europe/Berlin", 1) >= 0);
+        assert_se(setenv("TZ", ":Europe/Berlin", 1) >= 0);
         assert_se(!in_utc_timezone());
         assert_se(streq(tzname[0], "CET"));
         assert_se(streq(tzname[1], "CEST"));

src/timedate/timedatectl.c

@@ -46,7 +46,7 @@ typedef struct StatusInfo {
 } StatusInfo;
 
 static void print_status_info(const StatusInfo *i) {
-        const char *old_tz = NULL, *tz;
+        const char *old_tz = NULL, *tz, *tz_colon;
         bool have_time = false;
         char a[LINE_MAX];
         struct tm tm;
@@ -62,7 +62,8 @@ static void print_status_info(const StatusInfo *i) {
                 old_tz = strdupa(tz);
 
         /* Set the new $TZ */
-        if (setenv("TZ", isempty(i->timezone) ? "UTC" : i->timezone, true) < 0)
+        tz_colon = strjoina(":", isempty(i->timezone) ? "UTC" : i->timezone);
+        if (setenv("TZ", tz_colon, true) < 0)
                 log_warning_errno(errno, "Failed to set TZ environment variable, ignoring: %m");
         else
                 tzset();