diff --git a/src/basic/time-util.c b/src/basic/time-util.c
index e54c829623..40d1bf1e09 100644
--- a/src/basic/time-util.c
+++ b/src/basic/time-util.c
@@ -13,6 +13,7 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
+#include "hexdecoct.h"
 #include "io-util.h"
 #include "log.h"
 #include "parse-util.h"
@@ -624,16 +625,94 @@ char* format_timespan(char *buf, size_t l, usec_t t, usec_t accuracy) {
         return buf;
 }
 
+const char* get_tzname(bool dst) {
+        /* musl leaves the DST timezone name unset if there is no DST, map this back to no DST */
+        if (dst && isempty(tzname[1]))
+                dst = false;
+
+        return empty_to_null(tzname[dst]);
+}
+
 int parse_gmtoff(const char *t, long *ret) {
+        int r;
+
         assert(t);
 
         struct tm tm;
         const char *k = strptime(t, "%z", &tm);
-        if (!k || *k != '\0')
+        if (k && *k == '\0') {
+                /* Success! */
+                if (ret)
+                        *ret = tm.tm_gmtoff;
+                return 0;
+        }
+
+        /* musl v1.2.5 does not support %z specifier in strptime(). Since
+         * https://github.com/kraj/musl/commit/fced99e93daeefb0192fd16304f978d4401d1d77
+         * %z is supported, but it only supports strict RFC-822/ISO 8601 format, that is, 4 digits with sign
+         * (e.g. +0900 or -1400), but does not support extended format: 2 digits or colon separated 4 digits
+         * (e.g. +09 or -14:00). Let's add fallback logic to make it support the extended timezone spec. */
+
+        bool positive;
+        switch (*t) {
+        case '+':
+                positive = true;
+                break;
+        case '-':
+                positive = false;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        t++;
+        r = undecchar(*t);
+        if (r < 0)
+                return r;
+
+        usec_t u = r * 10 * USEC_PER_HOUR;
+
+        t++;
+        r = undecchar(*t);
+        if (r < 0)
+                return r;
+        u += r * USEC_PER_HOUR;
+
+        t++;
+        if (*t == '\0') /* 2 digits case */
+                goto finalize;
+
+        if (*t == ':') /* skip colon */
+                t++;
+
+        r = undecchar(*t);
+        if (r < 0)
+                return r;
+        if (r >= 6) /* refuse minutes equal to or larger than 60 */
                 return -EINVAL;
 
-        if (ret)
-                *ret = tm.tm_gmtoff;
+        u += r * 10 * USEC_PER_MINUTE;
+
+        t++;
+        r = undecchar(*t);
+        if (r < 0)
+                return r;
+
+        u += r * USEC_PER_MINUTE;
+
+        t++;
+        if (*t != '\0')
+                return -EINVAL;
+
+finalize:
+        if (u > USEC_PER_DAY) /* refuse larger than one day */
+                return -EINVAL;
+
+        if (ret) {
+                long gmtoff = u / USEC_PER_SEC;
+                *ret = positive ? gmtoff : -gmtoff;
+        }
+
         return 0;
 }
 
@@ -810,7 +889,11 @@ static int parse_timestamp_impl(
                 if (!k || *k != ' ')
                         continue;
 
+#ifdef __GLIBC__
+                /* musl does not set tm_wday field and set 0 unless it is explicitly requested by %w or so.
+                 * In the below, let's only check tm_wday field only when built with glibc. */
                 weekday = day->nr;
+#endif
                 t = k + 1;
                 break;
         }
@@ -1007,10 +1090,7 @@ int parse_timestamp(const char *t, usec_t *ret) {
          * not follow the timezone change in the current area. */
         tzset();
         for (int j = 0; j <= 1; j++) {
-                if (isempty(tzname[j]))
-                        continue;
-
-                if (!streq(tz, tzname[j]))
+                if (!streq_ptr(tz, get_tzname(j)))
                         continue;
 
                 /* The specified timezone matches tzname[] of the local timezone. */
diff --git a/src/basic/time-util.h b/src/basic/time-util.h
index 322a2ece6b..b5530e3e92 100644
--- a/src/basic/time-util.h
+++ b/src/basic/time-util.h
@@ -149,6 +149,7 @@ static inline char* format_timestamp(char *buf, size_t l, usec_t t) {
 #define FORMAT_TIMESTAMP_STYLE(t, style) \
         format_timestamp_style((char[FORMAT_TIMESTAMP_MAX]){}, FORMAT_TIMESTAMP_MAX, t, style)
 
+const char* get_tzname(bool dst);
 int parse_gmtoff(const char *t, long *ret);
 int parse_timestamp(const char *t, usec_t *ret);
 
diff --git a/src/core/manager.c b/src/core/manager.c
index 90a3f25aeb..b501d3f1c5 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -3208,7 +3208,7 @@ static int manager_dispatch_timezone_change(
         /* Read the new timezone */
         tzset();
 
-        log_debug("Timezone has been changed (now: %s).", tzname[daylight]);
+        log_debug("Timezone has been changed (now: %s).", get_tzname(daylight));
 
         HASHMAP_FOREACH(u, m->units)
                 if (UNIT_VTABLE(u)->timezone_change)
diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c
index 0e12e55a97..ed8e202a2e 100644
--- a/src/shared/calendarspec.c
+++ b/src/shared/calendarspec.c
@@ -370,9 +370,10 @@ int calendar_spec_to_string(const CalendarSpec *c, char **ret) {
 
                 tzset();
 
-                if (!isempty(tzname[c->dst])) {
+                const char *z = get_tzname(c->dst);
+                if (z) {
                         fputc(' ', f);
-                        fputs(tzname[c->dst], f);
+                        fputs(z, f);
                 }
         }
 
@@ -897,10 +898,11 @@ int calendar_spec_from_string(const char *p, CalendarSpec **ret) {
 
                 /* Check if the local timezone was specified? */
                 for (j = 0; j <= 1; j++) {
-                        if (isempty(tzname[j]))
+                        const char *z = get_tzname(j);
+                        if (!z)
                                 continue;
 
-                        e = endswith_no_case(p, tzname[j]);
+                        e = endswith_no_case(p, z);
                         if (!e)
                                 continue;
                         if (e == p)
diff --git a/src/test/test-time-util.c b/src/test/test-time-util.c
index 7bcf0ae7ee..f58be952ef 100644
--- a/src/test/test-time-util.c
+++ b/src/test/test-time-util.c
@@ -15,7 +15,7 @@
 static void set_timezone(const char *tz) {
         ASSERT_OK(set_unset_env("TZ", tz, /* overwrite = */ true));
         tzset();
-        log_info("TZ=%s, tzname[0]=%s, tzname[1]=%s", strna(getenv("TZ")), strempty(tzname[0]), strempty(tzname[1]));
+        log_info("TZ=%s, tzname[0]=%s, tzname[1]=%s", strna(getenv("TZ")), strempty(get_tzname(/* dst= */ false)), strempty(get_tzname(/* dst= */ true)));
 }
 
 TEST(parse_sec) {
@@ -400,6 +400,28 @@ static void test_format_timestamp_impl(usec_t x) {
         const char *xx = FORMAT_TIMESTAMP(x);
         ASSERT_NOT_NULL(xx);
 
+        /* Because of the timezone change, format_timestamp() may set timezone that is currently unused.
+         * E.g. Africa/Juba uses EAT since Sat Jan 15 10:00:00 2000 and until Sun Jan 31 20:59:59 2021, but
+         * now CAT/CAST is used there (see zdump for more details). In such cases, format_timestamp() may set
+         * the timezone used at the specified time (which happens when built with musl), but it may not match
+         * the timezone currently used, thus we may not parse back the timestamp. */
+
+        const char *space;
+        ASSERT_NOT_NULL(space = strrchr(xx, ' '));
+
+        const char *tz = space + 1;
+        if (!streq_ptr(tz, get_tzname(/* dst= */ false)) &&
+            !streq_ptr(tz, get_tzname(/* dst= */ true)) &&
+            parse_gmtoff(tz, NULL) < 0) {
+
+                log_warning("@" USEC_FMT " → %s, timezone '%s' is currently unused, ignoring.", x, xx, tz);
+
+                /* Verify the generated string except for the timezone part. Of course, in most cases, parsed
+                 * time does not match with the input, hence only check if it is parsable. */
+                ASSERT_OK(parse_timestamp(strndupa_safe(xx, space - xx), NULL));
+                return;
+        }
+
         usec_t y;
         ASSERT_OK(parse_timestamp(xx, &y));
         const char *yy = FORMAT_TIMESTAMP(y);
@@ -1109,15 +1131,15 @@ TEST(in_utc_timezone) {
 
         assert_se(setenv("TZ", "UTC", 1) >= 0);
         assert_se(in_utc_timezone());
-        ASSERT_STREQ(tzname[0], "UTC");
-        ASSERT_STREQ(tzname[1], "UTC");
+        ASSERT_STREQ(get_tzname(/* dst= */ false), "UTC");
+        ASSERT_STREQ(get_tzname(/* dst= */ true), "UTC");
         assert_se(timezone == 0);
         assert_se(daylight == 0);
 
         assert_se(setenv("TZ", "Europe/Berlin", 1) >= 0);
         assert_se(!in_utc_timezone());
-        ASSERT_STREQ(tzname[0], "CET");
-        ASSERT_STREQ(tzname[1], "CEST");
+        ASSERT_STREQ(get_tzname(/* dst= */ false), "CET");
+        ASSERT_STREQ(get_tzname(/* dst= */ true), "CEST");
 }
 
 TEST(map_clock_usec) {
diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
index 6e21d1a73a..9016f6c4a6 100644
--- a/src/timedate/timedated.c
+++ b/src/timedate/timedated.c
@@ -733,9 +733,9 @@ static int method_set_timezone(sd_bus_message *m, void *userdata, sd_bus_error *
         log_struct(LOG_INFO,
                    LOG_MESSAGE_ID(SD_MESSAGE_TIMEZONE_CHANGE_STR),
                    LOG_ITEM("TIMEZONE=%s", c->zone),
-                   LOG_ITEM("TIMEZONE_SHORTNAME=%s", tzname[daylight]),
+                   LOG_ITEM("TIMEZONE_SHORTNAME=%s", get_tzname(daylight)),
                    LOG_ITEM("DAYLIGHT=%i", daylight),
-                   LOG_MESSAGE("Changed time zone to '%s' (%s).", c->zone, tzname[daylight]));
+                   LOG_MESSAGE("Changed time zone to '%s' (%s).", c->zone, get_tzname(daylight)));
 
         (void) sd_bus_emit_properties_changed(sd_bus_message_get_bus(m),
                                               "/org/freedesktop/timedate1", "org.freedesktop.timedate1", "Timezone",