diff --git a/ports/unix/modtime.c b/ports/unix/modtime.c
index 0a463014d..479d2a79d 100644
--- a/ports/unix/modtime.c
+++ b/ports/unix/modtime.c
@@ -161,6 +161,37 @@ STATIC mp_obj_t mod_time_localtime(size_t n_args, const mp_obj_t *args) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_time_localtime_obj, 0, 1, mod_time_localtime);
 
+STATIC mp_obj_t mod_time_mktime(mp_obj_t tuple) {
+    size_t len;
+    mp_obj_t *elem;
+    mp_obj_get_array(tuple, &len, &elem);
+
+    // localtime generates a tuple of len 8. CPython uses 9, so we accept both.
+    if (len < 8 || len > 9) {
+        mp_raise_TypeError("mktime needs a tuple of length 8 or 9");
+    }
+
+    struct tm time = {
+        .tm_year = mp_obj_get_int(elem[0]) - 1900,
+        .tm_mon = mp_obj_get_int(elem[1]) - 1,
+        .tm_mday = mp_obj_get_int(elem[2]),
+        .tm_hour = mp_obj_get_int(elem[3]),
+        .tm_min = mp_obj_get_int(elem[4]),
+        .tm_sec = mp_obj_get_int(elem[5]),
+    };
+    if (len == 9) {
+        time.tm_isdst = mp_obj_get_int(elem[8]);
+    } else {
+        time.tm_isdst = -1; // auto-detect
+    }
+    time_t ret = mktime(&time);
+    if (ret == -1) {
+        mp_raise_msg(&mp_type_OverflowError, "invalid mktime usage");
+    }
+    return mp_obj_new_int(ret);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(mod_time_mktime_obj, mod_time_mktime);
+
 STATIC const mp_rom_map_elem_t mp_module_time_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_utime) },
     { MP_ROM_QSTR(MP_QSTR_clock), MP_ROM_PTR(&mod_time_clock_obj) },
@@ -174,6 +205,7 @@ STATIC const mp_rom_map_elem_t mp_module_time_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_ticks_add), MP_ROM_PTR(&mp_utime_ticks_add_obj) },
     { MP_ROM_QSTR(MP_QSTR_ticks_diff), MP_ROM_PTR(&mp_utime_ticks_diff_obj) },
     { MP_ROM_QSTR(MP_QSTR_localtime), MP_ROM_PTR(&mod_time_localtime_obj) },
+    { MP_ROM_QSTR(MP_QSTR_mktime), MP_ROM_PTR(&mod_time_mktime_obj) },
 };
 
 STATIC MP_DEFINE_CONST_DICT(mp_module_time_globals, mp_module_time_globals_table);
diff --git a/tests/unix/time.py b/tests/unix/time.py
new file mode 100644
index 000000000..a96c3f5b6
--- /dev/null
+++ b/tests/unix/time.py
@@ -0,0 +1,44 @@
+try:
+    import utime as time
+except ImportError:
+    import time
+
+DAYS_PER_MONTH = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+tzseconds = -time.mktime((1970, 1, 1, 0, 0, 0, 0, 0, 0))
+
+def is_leap(year):
+    return (year % 4) == 0
+
+def test():
+    seconds = 0
+    wday = 3 # Jan 1, 1970 was a Thursday
+    for year in range(1970, 2038):
+        print("Testing %d" % year)
+        yday = 1
+        for month in range(1, 13):
+            if month == 2 and is_leap(year):
+                DAYS_PER_MONTH[2] = 29
+            else:
+                DAYS_PER_MONTH[2] = 28
+            for day in range(1, DAYS_PER_MONTH[month] + 1):
+                secs = time.mktime((year, month, day, 0, 0, 0, 0, 0, 0)) + tzseconds
+                if secs != seconds:
+                    print("mktime failed for %d-%02d-%02d got %d expected %d" % (year, month, day, secs, seconds))
+                    return
+                tuple = time.localtime(seconds)
+                secs = time.mktime(tuple)
+                if secs != seconds:
+                    print("localtime failed for %d-%02d-%02d got %d expected %d" % (year, month, day, secs, seconds))
+                    return
+                seconds += 86400
+                if yday != tuple[7]:
+                    print("locatime for %d-%02d-%02d got yday %d, expecting %d" % (year, month, day, tuple[7], yday))
+                    return
+                if wday != tuple[6]:
+                    print("locatime for %d-%02d-%02d got wday %d, expecting %d" % (year, month, day, tuple[6], wday))
+                    return
+                yday += 1
+                wday = (wday + 1) % 7
+
+test()