diff --git a/plugins/restful/license.c b/plugins/restful/license.c
index ca48afa4..7173fa30 100644
--- a/plugins/restful/license.c
+++ b/plugins/restful/license.c
@@ -36,6 +36,7 @@
 #include <time.h>
 
 #include "errcodes.h"
+#include "utils/asprintf.h"
 #include "utils/log.h"
 
 #include "license.h"
@@ -81,7 +82,7 @@ static uint64_t mktimestamp(struct tm dt)
     return (ret);
 }
 
-static uint64_t get_asn1_ts(ASN1_TIME *time)
+static uint64_t get_asn1_ts(ASN1_TIME *time, char **ts_str)
 {
     struct tm   t;
     const char *str = (const char *) time->data;
@@ -97,7 +98,11 @@ static uint64_t get_asn1_ts(ASN1_TIME *time)
                &t.tm_hour, &t.tm_min, &t.tm_sec);
     }
 
+    neu_asprintf(ts_str, "%4d-%02d-%02d %02d:%02d:%02d", t.tm_year, t.tm_mon,
+                 t.tm_mday, t.tm_hour, t.tm_min, t.tm_sec);
+
     t.tm_mon -= 1;
+
     /* Note: we did not adjust the time based on time zone information */
     return mktimestamp(t);
 }
@@ -245,9 +250,14 @@ static int extract_license(const char *license_fname, const char *pub_key,
 
     not_before      = X509_get_notBefore(cert);
     not_after       = X509_get_notAfter(cert);
-    license->since_ = get_asn1_ts(not_before);
-    license->until_ = get_asn1_ts(not_after);
+    license->since_ = get_asn1_ts(not_before, &license->since_str_);
+    license->until_ = get_asn1_ts(not_after, &license->until_str_);
     nlog_info("certificate expire date: %s", not_after->data);
+    if (NULL == license->since_str_ || NULL == license->until_str_) {
+        nlog_warn("cannot strdup");
+        rv = NEU_ERR_EINTERNAL;
+        goto final;
+    }
 
     subj = X509_get_subject_name(cert);
     for (i = 0; i < X509_NAME_entry_count(subj); i++) {
@@ -342,26 +352,15 @@ const char *plugin_bit_str(plugin_bit_e b)
 
 void license_print(license_t *license)
 {
-    struct tm   tm        = {};
-    char        start[16] = {};
-    char        end[16]   = {};
-    time_t      since     = license->since_;
-    time_t      until     = license->until_;
-    const char *fmt       = "%Y%m%dT%H%M%S";
-
-    gmtime_r(&since, &tm);
-    strftime(start, sizeof(start), fmt, &tm);
-    gmtime_r(&until, &tm);
-    strftime(end, sizeof(end), fmt, &tm);
-
     char flag[sizeof(license->plugin_flag_) * 2 + 1] = {};
     print_bitvec(flag, sizeof(flag), license->plugin_flag_,
                  sizeof(license->plugin_flag_));
 
     nlog_info("license `%s` for %s, from %s to %s, max_nodes:%" PRIu32
               ", max_node_tags:%" PRIu32 ", flag:0x%s",
-              license->fname_, license_type_str(license->type_), start, end,
-              license->max_nodes_, license->max_node_tags_, flag);
+              license->fname_, license_type_str(license->type_),
+              license->since_str_, license->until_str_, license->max_nodes_,
+              license->max_node_tags_, flag);
 }
 
 void license_init(license_t *license)
@@ -375,6 +374,8 @@ void license_init(license_t *license)
 
 void license_fini(license_t *license)
 {
+    free(license->since_str_);
+    free(license->until_str_);
     free(license->fname_);
     free(license->token_);
 }
@@ -423,6 +424,8 @@ int license_read(license_t *license, const char *fname)
 
     license_print(&lic);
 
+    free(license->since_str_);
+    free(license->until_str_);
     free(license->fname_);
     free(license->token_);
     *license = lic;
diff --git a/plugins/restful/license.h b/plugins/restful/license.h
index 97894775..71946551 100644
--- a/plugins/restful/license.h
+++ b/plugins/restful/license.h
@@ -93,7 +93,9 @@ typedef struct {
     license_type_e type_;                 // license type
     char *         fname_;                // license file name
     uint64_t       since_;                // not before
+    char *         since_str_;            //
     uint64_t       until_;                // not after
+    char *         until_str_;            //
     uint32_t       max_nodes_;            // max number of nodes
     uint32_t       max_node_tags_;        // max number of tags per node
     uint8_t        plugin_flag_[200 / 8]; // plugin enable/disable bits
diff --git a/plugins/restful/license_handle.c b/plugins/restful/license_handle.c
index cbed979e..d44b5790 100644
--- a/plugins/restful/license_handle.c
+++ b/plugins/restful/license_handle.c
@@ -135,17 +135,12 @@ int copy_license_file_if_necessary()
 
 void handle_get_license(nng_aio *aio)
 {
-    int                         rv              = 0;
-    char *                      license_path    = NULL;
-    license_t                   lic             = {};
-    neu_json_get_license_resp_t resp            = {};
-    time_t                      since           = 0;
-    time_t                      until           = 0;
-    char                        valid_since[20] = {};
-    char                        valid_until[20] = {};
-    struct tm                   tm              = {};
-    UT_array *                  plugin_names    = NULL;
-    char *                      result          = NULL;
+    int                         rv           = 0;
+    char *                      license_path = NULL;
+    license_t                   lic          = {};
+    neu_json_get_license_resp_t resp         = {};
+    UT_array *                  plugin_names = NULL;
+    char *                      result       = NULL;
 
     VALIDATE_JWT(aio);
 
@@ -163,26 +158,10 @@ void handle_get_license(nng_aio *aio)
         goto final;
     }
 
-    since = license_not_before(&lic);
-    gmtime_r(&since, &tm);
-    if (0 ==
-        strftime(valid_since, sizeof(valid_since), "%Y-%m-%d %H:%M:%S", &tm)) {
-        rv = NEU_ERR_EINTERNAL;
-        goto final;
-    }
-
-    until = license_not_after(&lic);
-    gmtime_r(&until, &tm);
-    if (0 ==
-        strftime(valid_until, sizeof(valid_until), "%Y-%m-%d %H:%M:%S", &tm)) {
-        rv = NEU_ERR_EINTERNAL;
-        goto final;
-    }
-
     resp.license_type  = (char *) license_type_str(license_get_type(&lic));
     resp.valid         = !license_is_expired(&lic);
-    resp.valid_since   = valid_since;
-    resp.valid_until   = valid_until;
+    resp.valid_since   = lic.since_str_;
+    resp.valid_until   = lic.until_str_;
     resp.max_nodes     = license_get_max_nodes(&lic);
     resp.max_node_tags = license_get_max_node_tags(&lic);