diff --git a/platform-independent/c/core/src/mpw-marshal-util.c b/platform-independent/c/core/src/mpw-marshal-util.c
index 4da45eb5..eca589c9 100644
--- a/platform-independent/c/core/src/mpw-marshal-util.c
+++ b/platform-independent/c/core/src/mpw-marshal-util.c
@@ -35,10 +35,11 @@ char *mpw_get_token(const char **in, const char *eol, char *delim) {
     return token;
 }
 
-time_t mpw_mktime(
+time_t mpw_timegm(
         const char *time) {
 
     // TODO: Support for parsing non-UTC time strings
+    // Parse time as a UTC timestamp, into a tm.
     struct tm tm = { .tm_isdst = -1 };
     if (time && sscanf( time, "%4d-%2d-%2dT%2d:%2d:%2dZ",
             &tm.tm_year, &tm.tm_mon, &tm.tm_mday,
@@ -46,8 +47,9 @@ time_t mpw_mktime(
         tm.tm_year -= 1900; // tm_year 0 = rfc3339 year  1900
         tm.tm_mon -= 1;     // tm_mon  0 = rfc3339 month 1
 
-        // mktime converts tm to local, setting tm_gmtoff; use it to offset the result back to UTC.
-        return mktime( &tm ) + tm.tm_gmtoff;
+        // mktime interprets tm as being local, we need to offset back to UTC (timegm/tm_gmtoff are non-standard).
+        time_t local_time = mktime( &tm ), local_dst = tm.tm_isdst > 0? 3600: 0;
+        return local_time + local_dst - mktime( gmtime( &local_time ) );
     }
 
     return false;
diff --git a/platform-independent/c/core/src/mpw-marshal-util.h b/platform-independent/c/core/src/mpw-marshal-util.h
index 3afbfb07..a4db76b6 100644
--- a/platform-independent/c/core/src/mpw-marshal-util.h
+++ b/platform-independent/c/core/src/mpw-marshal-util.h
@@ -34,7 +34,7 @@
 char *mpw_get_token(
         const char **in, const char *eol, char *delim);
 /** Convert an RFC 3339 time string into epoch time. */
-time_t mpw_mktime(
+time_t mpw_timegm(
         const char *time);
 
 /// JSON parsing.
diff --git a/platform-independent/c/core/src/mpw-marshal.c b/platform-independent/c/core/src/mpw-marshal.c
index cee7c948..e598779b 100644
--- a/platform-independent/c/core/src/mpw-marshal.c
+++ b/platform-independent/c/core/src/mpw-marshal.c
@@ -407,7 +407,7 @@ static void mpw_marshal_read_flat_info(
             if (strcmp( headerName, "Passwords" ) == 0)
                 info->redacted = strcmp( headerValue, "VISIBLE" ) != 0;
             if (strcmp( headerName, "Date" ) == 0)
-                info->date = mpw_mktime( headerValue );
+                info->date = mpw_timegm( headerValue );
 
             mpw_free_strings( &headerName, &headerValue, NULL );
             continue;
@@ -580,7 +580,7 @@ static MPMarshalledUser *mpw_marshal_read_flat(
                 return NULL;
             }
             MPAlgorithmVersion siteAlgorithm = (MPAlgorithmVersion)value;
-            time_t siteLastUsed = mpw_mktime( str_lastUsed );
+            time_t siteLastUsed = mpw_timegm( str_lastUsed );
             if (!siteLastUsed) {
                 *error = (MPMarshalError){ MPMarshalErrorIllegal, mpw_str( "Invalid site last used: %s: %s", siteName, str_lastUsed ) };
                 return NULL;
@@ -650,7 +650,7 @@ static void mpw_marshal_read_json_info(
     if (fileFormat < 1)
         return;
     info->redacted = mpw_get_json_boolean( json_file, "export.redacted", true );
-    info->date = mpw_mktime( mpw_get_json_string( json_file, "export.date", NULL ) );
+    info->date = mpw_timegm( mpw_get_json_string( json_file, "export.date", NULL ) );
 
     // Section: "user"
     info->algorithm = (MPAlgorithmVersion)mpw_get_json_int( json_file, "user.algorithm", MPAlgorithmVersionCurrent );
@@ -707,7 +707,7 @@ static MPMarshalledUser *mpw_marshal_read_json(
         *error = (MPMarshalError){ MPMarshalErrorIllegal, mpw_str( "Invalid user default type: %u", defaultType ) };
         return NULL;
     }
-    time_t lastUsed = mpw_mktime( str_lastUsed );
+    time_t lastUsed = mpw_timegm( str_lastUsed );
     if (!lastUsed) {
         *error = (MPMarshalError){ MPMarshalErrorIllegal, mpw_str( "Invalid user last used: %s", str_lastUsed ) };
         return NULL;
@@ -760,7 +760,7 @@ static MPMarshalledUser *mpw_marshal_read_json(
         MPResultType siteLoginType = (MPResultType)mpw_get_json_int( json_site.val, "login_type", MPResultTypeTemplateName );
         unsigned int siteUses = (unsigned int)mpw_get_json_int( json_site.val, "uses", 0 );
         str_lastUsed = mpw_get_json_string( json_site.val, "last_used", NULL );
-        time_t siteLastUsed = mpw_mktime( str_lastUsed );
+        time_t siteLastUsed = mpw_timegm( str_lastUsed );
         if (!siteLastUsed) {
             *error = (MPMarshalError){ MPMarshalErrorIllegal, mpw_str( "Invalid site last used: %s: %s", siteName, str_lastUsed ) };
             return NULL;