shared/timeutils: Standardize supported date range on all platforms.

This is code makes sure that time functions work properly on a
reasonable date range, on all platforms, regardless of the epoch.
The suggested minimum range is 1970 to 2099.

In order to reduce code footprint, code to support far away dates
is only enabled specified by the port.

New types are defined to identify timestamps.

The implementation with the smallest code footprint is when
support timerange is limited to 1970-2099 and Epoch is 1970.
This makes it possible to use 32 bit unsigned integers for
all timestamps.

On ARM4F, adding support for dates up to year 3000 adds
460 bytes of code. Supporting dates back to 1600 adds
another 44 bytes of code.

Signed-off-by: Yoctopuce dev <dev@yoctopuce.com>

extmod/modtime.c

@@ -58,7 +58,7 @@ static mp_obj_t time_localtime(size_t n_args, const mp_obj_t *args) {
         return mp_time_localtime_get();
     } else {
         // Convert given seconds to tuple.
-        mp_int_t seconds = mp_obj_get_int(args[0]);
+        mp_timestamp_t seconds = timeutils_obj_get_timestamp(args[0]);
         timeutils_struct_time_t tm;
         timeutils_seconds_since_epoch_to_struct_time(seconds, &tm);
         mp_obj_t tuple[8] = {
@@ -90,7 +90,7 @@ static mp_obj_t time_mktime(mp_obj_t tuple) {
         mp_raise_TypeError(MP_ERROR_TEXT("mktime needs a tuple of length 8 or 9"));
     }
 
-    return mp_obj_new_int_from_uint(timeutils_mktime(mp_obj_get_int(elem[0]),
+    return timeutils_obj_from_timestamp(timeutils_mktime(mp_obj_get_int(elem[0]),
         mp_obj_get_int(elem[1]), mp_obj_get_int(elem[2]), mp_obj_get_int(elem[3]),
         mp_obj_get_int(elem[4]), mp_obj_get_int(elem[5])));
 }

extmod/vfs_fat.c

@@ -326,7 +326,7 @@ static mp_obj_t fat_vfs_stat(mp_obj_t vfs_in, mp_obj_t path_in) {
     } else {
         mode |= MP_S_IFREG;
     }
-    mp_int_t seconds = timeutils_seconds_since_epoch(
+    mp_timestamp_t seconds = timeutils_seconds_since_epoch(
         1980 + ((fno.fdate >> 9) & 0x7f),
         (fno.fdate >> 5) & 0x0f,
         fno.fdate & 0x1f,
@@ -341,9 +341,9 @@ static mp_obj_t fat_vfs_stat(mp_obj_t vfs_in, mp_obj_t path_in) {
     t->items[4] = MP_OBJ_NEW_SMALL_INT(0); // st_uid
     t->items[5] = MP_OBJ_NEW_SMALL_INT(0); // st_gid
     t->items[6] = mp_obj_new_int_from_uint(fno.fsize); // st_size
-    t->items[7] = mp_obj_new_int_from_uint(seconds); // st_atime
-    t->items[8] = mp_obj_new_int_from_uint(seconds); // st_mtime
-    t->items[9] = mp_obj_new_int_from_uint(seconds); // st_ctime
+    t->items[7] = timeutils_obj_from_timestamp(seconds); // st_atime
+    t->items[8] = timeutils_obj_from_timestamp(seconds); // st_mtime
+    t->items[9] = timeutils_obj_from_timestamp(seconds); // st_ctime
 
     return MP_OBJ_FROM_PTR(t);
 }

extmod/vfs_lfsx.c

@@ -378,7 +378,7 @@ static mp_obj_t MP_VFS_LFSx(stat)(mp_obj_t self_in, mp_obj_t path_in) {
         mp_raise_OSError(-ret);
     }
 
-    mp_uint_t mtime = 0;
+    mp_timestamp_t mtime = 0;
     #if LFS_BUILD_VERSION == 2
     uint8_t mtime_buf[8];
     lfs2_ssize_t sz = lfs2_getattr(&self->lfs, path, LFS_ATTR_MTIME, &mtime_buf, sizeof(mtime_buf));
@@ -400,9 +400,9 @@ static mp_obj_t MP_VFS_LFSx(stat)(mp_obj_t self_in, mp_obj_t path_in) {
     t->items[4] = MP_OBJ_NEW_SMALL_INT(0); // st_uid
     t->items[5] = MP_OBJ_NEW_SMALL_INT(0); // st_gid
     t->items[6] = mp_obj_new_int_from_uint(info.size); // st_size
-    t->items[7] = mp_obj_new_int_from_uint(mtime); // st_atime
-    t->items[8] = mp_obj_new_int_from_uint(mtime); // st_mtime
-    t->items[9] = mp_obj_new_int_from_uint(mtime); // st_ctime
+    t->items[7] = timeutils_obj_from_timestamp(mtime); // st_atime
+    t->items[8] = timeutils_obj_from_timestamp(mtime); // st_mtime
+    t->items[9] = timeutils_obj_from_timestamp(mtime); // st_ctime
 
     return MP_OBJ_FROM_PTR(t);
 }

ports/cc3200/mods/modtime.c

@@ -50,5 +50,5 @@ static mp_obj_t mp_time_localtime_get(void) {
 
 // Returns the number of seconds, as an integer, since the Epoch.
 static mp_obj_t mp_time_time_get(void) {
-    return mp_obj_new_int(pyb_rtc_get_seconds());
+    return timeutils_obj_from_timestamp(pyb_rtc_get_seconds());
 }

ports/esp32/modtime.c

@@ -54,5 +54,5 @@ static mp_obj_t mp_time_localtime_get(void) {
 static mp_obj_t mp_time_time_get(void) {
     struct timeval tv;
     gettimeofday(&tv, NULL);
-    return mp_obj_new_int(tv.tv_sec);
+    return timeutils_obj_from_timestamp(tv.tv_sec);
 }

ports/esp8266/modtime.c

@@ -31,7 +31,7 @@
 
 // Return the localtime as an 8-tuple.
 static mp_obj_t mp_time_localtime_get(void) {
-    mp_int_t seconds = pyb_rtc_get_us_since_epoch() / 1000 / 1000;
+    mp_uint_t seconds = pyb_rtc_get_us_since_epoch() / 1000u / 1000u;
     timeutils_struct_time_t tm;
     timeutils_seconds_since_epoch_to_struct_time(seconds, &tm);
     mp_obj_t tuple[8] = {
@@ -50,5 +50,5 @@ static mp_obj_t mp_time_localtime_get(void) {
 // Returns the number of seconds, as an integer, since the Epoch.
 static mp_obj_t mp_time_time_get(void) {
     // get date and time
-    return mp_obj_new_int(pyb_rtc_get_us_since_epoch() / 1000 / 1000);
+    return timeutils_obj_from_timestamp(pyb_rtc_get_us_since_epoch() / 1000 / 1000);
 }

ports/mimxrt/modtime.c

@@ -51,14 +51,7 @@ static mp_obj_t mp_time_localtime_get(void) {
 static mp_obj_t mp_time_time_get(void) {
     snvs_lp_srtc_datetime_t t;
     SNVS_LP_SRTC_GetDatetime(SNVS, &t);
-    // EPOCH is 1970 for this port, which leads to the following trouble:
-    // timeutils_seconds_since_epoch() calls timeutils_seconds_since_2000(), and
-    // timeutils_seconds_since_2000() subtracts 2000 from year, but uses
-    // an unsigned number for seconds, That causes an underrun, which is not
-    // fixed by adding the TIMEUTILS_SECONDS_1970_TO_2000.
-    // Masking it to 32 bit for year < 2000 fixes it.
-    return mp_obj_new_int_from_ull(
+    return timeutils_obj_from_timestamp(
         timeutils_seconds_since_epoch(t.year, t.month, t.day, t.hour, t.minute, t.second)
-        & (t.year < 2000 ? 0xffffffff : 0xffffffffffff)
         );
 }

ports/renesas-ra/modtime.c

@@ -53,5 +53,5 @@ static mp_obj_t mp_time_time_get(void) {
     rtc_init_finalise();
     ra_rtc_t time;
     ra_rtc_get_time(&time);
-    return mp_obj_new_int(timeutils_seconds_since_epoch(time.year, time.month, time.date, time.hour, time.minute, time.second));
+    return timeutils_obj_from_timestamp(timeutils_seconds_since_epoch(time.year, time.month, time.date, time.hour, time.minute, time.second));
 }

ports/stm32/modtime.c

@@ -59,5 +59,5 @@ static mp_obj_t mp_time_time_get(void) {
     RTC_TimeTypeDef time;
     HAL_RTC_GetTime(&RTCHandle, &time, RTC_FORMAT_BIN);
     HAL_RTC_GetDate(&RTCHandle, &date, RTC_FORMAT_BIN);
-    return mp_obj_new_int(timeutils_seconds_since_epoch(2000 + date.Year, date.Month, date.Date, time.Hours, time.Minutes, time.Seconds));
+    return timeutils_obj_from_timestamp(timeutils_seconds_since_epoch(2000 + date.Year, date.Month, date.Date, time.Hours, time.Minutes, time.Seconds));
 }

ports/stm32/mpconfigport.h

@@ -76,6 +76,7 @@
 #ifndef MICROPY_FLOAT_IMPL // can be configured by each board via mpconfigboard.mk
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_FLOAT)
 #endif
+#define MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE (1)
 #define MICROPY_USE_INTERNAL_ERRNO  (1)
 #define MICROPY_SCHEDULER_STATIC_NODES (1)
 #define MICROPY_SCHEDULER_DEPTH     (8)

ports/unix/Makefile

@@ -52,6 +52,10 @@ CFLAGS += $(INC) $(CWARN) -std=gnu99 -DUNIX $(COPT) -I$(VARIANT_DIR) $(CFLAGS_EX
 # This option has no effect on 64-bit builds.
 CFLAGS += -D_FILE_OFFSET_BITS=64
 
+# Force the use of 64-bits for time_t in C library functions on 32-bit platforms.
+# This option has no effect on 64-bit builds.
+CFLAGS += -D_TIME_BITS=64
+
 # Debugging/Optimization
 ifdef DEBUG
 COPT ?= -Og

ports/unix/modtime.c

@@ -34,6 +34,7 @@
 
 #include "py/mphal.h"
 #include "py/runtime.h"
+#include "shared/timeutils/timeutils.h"
 
 #ifdef _WIN32
 static inline int msec_sleep_tv(struct timeval *tv) {
@@ -130,12 +131,7 @@ static mp_obj_t mod_time_gm_local_time(size_t n_args, const mp_obj_t *args, stru
     if (n_args == 0) {
         t = time(NULL);
     } else {
-        #if MICROPY_PY_BUILTINS_FLOAT && MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
-        mp_float_t val = mp_obj_get_float(args[0]);
-        t = (time_t)MICROPY_FLOAT_C_FUN(trunc)(val);
-        #else
-        t = mp_obj_get_int(args[0]);
-        #endif
+        t = (time_t)timeutils_obj_get_timestamp(args[0]);
     }
     struct tm *tm = time_func(&t);
 
@@ -196,7 +192,7 @@ static mp_obj_t mod_time_mktime(mp_obj_t tuple) {
     if (ret == -1) {
         mp_raise_msg(&mp_type_OverflowError, MP_ERROR_TEXT("invalid mktime usage"));
     }
-    return mp_obj_new_int(ret);
+    return timeutils_obj_from_timestamp(ret);
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mod_time_mktime_obj, mod_time_mktime);
 

ports/unix/mpconfigport.h

@@ -124,6 +124,9 @@ typedef long mp_off_t;
 // VFS stat functions should return time values relative to 1970/1/1
 #define MICROPY_EPOCH_IS_1970       (1)
 
+// port modtime functions use time_t
+#define MICROPY_TIMESTAMP_IMPL      (MICROPY_TIMESTAMP_IMPL_TIME_T)
+
 // Assume that select() call, interrupted with a signal, and erroring
 // with EINTR, updates remaining timeout value.
 #define MICROPY_SELECT_REMAINING_TIME (1)

ports/windows/Makefile

@@ -46,6 +46,10 @@ LDFLAGS += -lm -lbcrypt $(LDFLAGS_EXTRA)
 # This option has no effect on 64-bit builds.
 CFLAGS += -D_FILE_OFFSET_BITS=64
 
+# Force the use of 64-bits for time_t in C library functions on 32-bit platforms.
+# This option has no effect on 64-bit builds.
+CFLAGS += -D_TIME_BITS=64
+
 # Debugging/Optimization
 ifdef DEBUG
 CFLAGS += -g

py/mpconfig.h

@@ -893,6 +893,64 @@ typedef double mp_float_t;
 #define MICROPY_FULL_CHECKS (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_CORE_FEATURES)
 #endif
 
+// Ports can choose to use timestamps based on 2000-01-01 or 1970-01-01
+// Default is timestamps based on 2000-01-01
+#if !defined(MICROPY_EPOCH_IS_2000) && !defined(MICROPY_EPOCH_IS_1970)
+#define MICROPY_EPOCH_IS_2000 (1)
+#define MICROPY_EPOCH_IS_1970 (0)
+#elif !defined(MICROPY_EPOCH_IS_1970)
+#define MICROPY_EPOCH_IS_1970 (1 - (MICROPY_EPOCH_IS_2000))
+#elif !defined(MICROPY_EPOCH_IS_2000)
+#define MICROPY_EPOCH_IS_2000 (1 - (MICROPY_EPOCH_IS_1970))
+#endif
+
+// To maintain reasonable compatibility with CPython on embedded systems,
+// and avoid breaking anytime soon, time functions are defined to work
+// at least between 1970 and 2099 (included) on any machine.
+//
+// Specific ports can enable extended date support
+// - after 2099 using MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND
+// - before 1970 using MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+// The largest possible range is year 1600 to year 3000
+//
+// By default, extended date support is only enabled for machines using 64 bit pointers,
+// but it can be enabled by specific ports
+#ifndef MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+#if MP_SSIZE_MAX > 2147483647
+#define MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE (1)
+#else
+#define MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE (0)
+#endif
+#endif
+
+// When support for dates <1970 is enabled, supporting >=2100 does not cost anything
+#ifndef MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND
+#define MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND (MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE)
+#endif
+
+// The type to be used to represent platform-specific timestamps depends on the choices above
+#define MICROPY_TIMESTAMP_IMPL_LONG_LONG (0)
+#define MICROPY_TIMESTAMP_IMPL_UINT (1)
+#define MICROPY_TIMESTAMP_IMPL_TIME_T (2)
+
+#ifndef MICROPY_TIMESTAMP_IMPL
+#if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE || MICROPY_EPOCH_IS_2000
+#define MICROPY_TIMESTAMP_IMPL (MICROPY_TIMESTAMP_IMPL_LONG_LONG)
+#else
+#define MICROPY_TIMESTAMP_IMPL (MICROPY_TIMESTAMP_IMPL_UINT)
+#endif
+#endif
+
+// `mp_timestamp_t` is the type that should be used by the port
+// to represent timestamps, and is referenced to the platform epoch
+#if MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_LONG_LONG
+typedef long long mp_timestamp_t;
+#elif MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_UINT
+typedef mp_uint_t mp_timestamp_t;
+#elif MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_TIME_T
+typedef time_t mp_timestamp_t;
+#endif
+
 // Whether POSIX-semantics non-blocking streams are supported
 #ifndef MICROPY_STREAMS_NON_BLOCK
 #define MICROPY_STREAMS_NON_BLOCK (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)

shared/timeutils/timeutils.c

@@ -29,12 +29,27 @@
 
 #include "shared/timeutils/timeutils.h"
 
-// LEAPOCH corresponds to 2000-03-01, which is a mod-400 year, immediately
-// after Feb 29. We calculate seconds as a signed integer relative to that.
+// To maintain reasonable compatibility with CPython on embedded systems,
+// and avoid breaking anytime soon, timeutils functions are required to
+// work properly between 1970 and 2099 on all ports.
 //
-// Our timebase is relative to 2000-01-01.
+// During that period of time, leap years occur every 4 years without
+// exception, so we can keep the code short for 32 bit machines.
 
-#define LEAPOCH ((31 + 29) * 86400)
+// The last leap day before the required period is Feb 29, 1968.
+// This is the number of days to add to get to that date.
+#define PREV_LEAP_DAY  ((mp_uint_t)(365 + 366 - (31 + 29)))
+#define PREV_LEAP_YEAR 1968
+
+// On ports where either MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND or
+// MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE is enabled, we include extra
+// code to support leap years outside of the 'easy' period.
+// Computation is then made based on 1600 (a mod-400 year).
+// This is the number of days between 1600 and 1968.
+#define QC_BASE_DAY  134409
+#define QC_LEAP_YEAR 1600
+// This is the number of leap days between 1600 and 1970
+#define QC_LEAP_DAYS 89
 
 #define DAYS_PER_400Y (365 * 400 + 97)
 #define DAYS_PER_100Y (365 * 100 + 24)
@@ -42,8 +57,20 @@
 
 static const uint16_t days_since_jan1[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
 
+// type used internally to count small integers relative to epoch
+// (using uint when possible produces smaller code on some platforms)
+#if MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+typedef mp_int_t relint_t;
+#else
+typedef mp_uint_t relint_t;
+#endif
+
 bool timeutils_is_leap_year(mp_uint_t year) {
+    #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
     return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
+    #else
+    return year % 4 == 0;
+    #endif
 }
 
 // month is one based
@@ -65,67 +92,67 @@ mp_uint_t timeutils_year_day(mp_uint_t year, mp_uint_t month, mp_uint_t date) {
     return yday;
 }
 
-void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t, timeutils_struct_time_t *tm) {
-    // The following algorithm was adapted from musl's __secs_to_tm and adapted
-    // for differences in MicroPython's timebase.
+void timeutils_seconds_since_1970_to_struct_time(timeutils_timestamp_t seconds, timeutils_struct_time_t *tm) {
+    // The following algorithm was inspired from musl's __secs_to_tm
+    // and simplified to reduce code footprint in the simple case
 
-    mp_int_t seconds = t - LEAPOCH;
-
-    mp_int_t days = seconds / 86400;
+    relint_t days = seconds / 86400;
     seconds %= 86400;
+    #if MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
     if (seconds < 0) {
         seconds += 86400;
         days -= 1;
     }
+    #endif
     tm->tm_hour = seconds / 3600;
     tm->tm_min = seconds / 60 % 60;
     tm->tm_sec = seconds % 60;
 
-    mp_int_t wday = (days + 2) % 7;   // Mar 1, 2000 was a Wednesday (2)
+    relint_t wday = (days + 3) % 7;   // Jan 1, 1970 was a Thursday (3)
+    #if MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
     if (wday < 0) {
         wday += 7;
     }
+    #endif
     tm->tm_wday = wday;
 
-    mp_int_t qc_cycles = days / DAYS_PER_400Y;
+    days += PREV_LEAP_DAY;
+
+    #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+    // rebase day to the oldest supported date (=> always positive)
+    mp_uint_t base_year = QC_LEAP_YEAR;
+    days += QC_BASE_DAY;
+    mp_uint_t qc_cycles = days / DAYS_PER_400Y;
     days %= DAYS_PER_400Y;
-    if (days < 0) {
-        days += DAYS_PER_400Y;
-        qc_cycles--;
-    }
-    mp_int_t c_cycles = days / DAYS_PER_100Y;
+    mp_uint_t c_cycles = days / DAYS_PER_100Y;
     if (c_cycles == 4) {
         c_cycles--;
     }
     days -= (c_cycles * DAYS_PER_100Y);
+    #else
+    mp_uint_t base_year = PREV_LEAP_YEAR;
+    mp_uint_t qc_cycles = 0;
+    mp_uint_t c_cycles = 0;
+    #endif
 
-    mp_int_t q_cycles = days / DAYS_PER_4Y;
+    mp_uint_t q_cycles = days / DAYS_PER_4Y;
+    #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
     if (q_cycles == 25) {
         q_cycles--;
     }
+    #endif
     days -= q_cycles * DAYS_PER_4Y;
 
-    mp_int_t years = days / 365;
+    relint_t years = days / 365;
     if (years == 4) {
         years--;
     }
     days -= (years * 365);
 
-    /* We will compute tm_yday at the very end
-    mp_int_t leap = !years && (q_cycles || !c_cycles);
-
-    tm->tm_yday = days + 31 + 28 + leap;
-    if (tm->tm_yday >= 365 + leap) {
-        tm->tm_yday -= 365 + leap;
-    }
-
-    tm->tm_yday++;  // Make one based
-    */
-
-    tm->tm_year = 2000 + years + 4 * q_cycles + 100 * c_cycles + 400 * qc_cycles;
+    tm->tm_year = base_year + years + 4 * q_cycles + 100 * c_cycles + 400 * qc_cycles;
 
     // Note: days_in_month[0] corresponds to March
-    static const int8_t days_in_month[] = {31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29};
+    static const uint8_t days_in_month[] = {31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31, 29};
 
     mp_int_t month;
     for (month = 0; days_in_month[month] <= days; month++) {
@@ -144,21 +171,28 @@ void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t, timeutils_struct_t
 }
 
 // returns the number of seconds, as an integer, since 2000-01-01
-mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
+timeutils_timestamp_t timeutils_seconds_since_1970(mp_uint_t year, mp_uint_t month,
     mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
-    return
-        second
-        + minute * 60
-        + hour * 3600
-        + (timeutils_year_day(year, month, date) - 1
-            + ((year - 2000 + 3) / 4) // add a day each 4 years starting with 2001
-            - ((year - 2000 + 99) / 100) // subtract a day each 100 years starting with 2001
-            + ((year - 2000 + 399) / 400) // add a day each 400 years starting with 2001
-            ) * 86400
-        + (year - 2000) * 31536000;
+    #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+    mp_uint_t ref_year = QC_LEAP_YEAR;
+    #else
+    mp_uint_t ref_year = PREV_LEAP_YEAR;
+    #endif
+    timeutils_timestamp_t res;
+    res = ((relint_t)year - 1970) * 365;
+    res += (year - (ref_year + 1)) / 4; // add a day each 4 years
+    #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+    res -= (year - (ref_year + 1)) / 100; // subtract a day each 100 years
+    res += (year - (ref_year + 1)) / 400; // add a day each 400 years
+    res -= QC_LEAP_DAYS;
+    #endif
+    res += timeutils_year_day(year, month, date) - 1;
+    res *= 86400;
+    res += hour * 3600 + minute * 60 + second;
+    return res;
 }
 
-mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
+timeutils_timestamp_t timeutils_mktime_1970(mp_uint_t year, mp_int_t month, mp_int_t mday,
     mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
 
     // Normalize the tuple. This allows things like:
@@ -211,12 +245,16 @@ mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
             year++;
         }
     }
-    return timeutils_seconds_since_2000(year, month, mday, hours, minutes, seconds);
+    return timeutils_seconds_since_1970(year, month, mday, hours, minutes, seconds);
 }
 
 // Calculate the weekday from the date.
 // The result is zero based with 0 = Monday.
 // by Michael Keith and Tom Craver, 1990.
 int timeutils_calc_weekday(int y, int m, int d) {
-    return ((d += m < 3 ? y-- : y - 2, 23 * m / 9 + d + 4 + y / 4 - y / 100 + y / 400) + 6) % 7;
+    return ((d += m < 3 ? y-- : y - 2, 23 * m / 9 + d + 4 + y / 4
+        #if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+        - y / 100 + y / 400
+        #endif
+        ) + 6) % 7;
 }

shared/timeutils/timeutils.h

@@ -27,9 +27,23 @@
 #ifndef MICROPY_INCLUDED_LIB_TIMEUTILS_TIMEUTILS_H
 #define MICROPY_INCLUDED_LIB_TIMEUTILS_TIMEUTILS_H
 
+#include "py/obj.h"
+#if MICROPY_PY_BUILTINS_FLOAT && MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+#include <math.h> // required for trunc()
+#endif
+
+// `timeutils_timestamp_t` is the type used internally by timeutils to
+// represent timestamps, and is always referenced to 1970.
+// It may not match the platform-specific `mp_timestamp_t`.
+#if MICROPY_TIME_SUPPORT_Y2100_AND_BEYOND || MICROPY_TIME_SUPPORT_Y1969_AND_BEFORE
+typedef long long timeutils_timestamp_t;
+#else
+typedef mp_uint_t timeutils_timestamp_t;
+#endif
+
 // The number of seconds between 1970/1/1 and 2000/1/1 is calculated using:
 // time.mktime((2000,1,1,0,0,0,0,0,0)) - time.mktime((1970,1,1,0,0,0,0,0,0))
-#define TIMEUTILS_SECONDS_1970_TO_2000 (946684800ULL)
+#define TIMEUTILS_SECONDS_1970_TO_2000 (946684800LL)
 
 typedef struct _timeutils_struct_time_t {
     uint16_t tm_year;       // i.e. 2014
@@ -45,66 +59,116 @@ typedef struct _timeutils_struct_time_t {
 bool timeutils_is_leap_year(mp_uint_t year);
 mp_uint_t timeutils_days_in_month(mp_uint_t year, mp_uint_t month);
 mp_uint_t timeutils_year_day(mp_uint_t year, mp_uint_t month, mp_uint_t date);
+int timeutils_calc_weekday(int y, int m, int d);
 
-void timeutils_seconds_since_2000_to_struct_time(mp_uint_t t,
+void timeutils_seconds_since_1970_to_struct_time(timeutils_timestamp_t t,
     timeutils_struct_time_t *tm);
 
 // Year is absolute, month/date are 1-based, hour/minute/second are 0-based.
-mp_uint_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month,
+timeutils_timestamp_t timeutils_seconds_since_1970(mp_uint_t year, mp_uint_t month,
     mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second);
 
 // Year is absolute, month/mday are 1-based, hours/minutes/seconds are 0-based.
-mp_uint_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
+timeutils_timestamp_t timeutils_mktime_1970(mp_uint_t year, mp_int_t month, mp_int_t mday,
     mp_int_t hours, mp_int_t minutes, mp_int_t seconds);
 
+static inline mp_timestamp_t timeutils_obj_get_timestamp(mp_obj_t o_in) {
+    #if MICROPY_PY_BUILTINS_FLOAT && MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+    mp_float_t val = mp_obj_get_float(o_in);
+    return (mp_timestamp_t)MICROPY_FLOAT_C_FUN(trunc)(val);
+    #elif MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_UINT
+    return mp_obj_get_uint(o_in);
+    #else
+    return mp_obj_get_ll(o_in);
+    #endif
+}
+
+static inline mp_obj_t timeutils_obj_from_timestamp(mp_timestamp_t t) {
+    #if MICROPY_TIMESTAMP_IMPL == MICROPY_TIMESTAMP_IMPL_UINT
+    return mp_obj_new_int_from_uint(t);
+    #else
+    return mp_obj_new_int_from_ll(t);
+    #endif
+}
+
+static inline void timeutils_seconds_since_2000_to_struct_time(mp_timestamp_t t, timeutils_struct_time_t *tm) {
+    timeutils_seconds_since_1970_to_struct_time((timeutils_timestamp_t)(t + TIMEUTILS_SECONDS_1970_TO_2000), tm);
+}
+
+// Year is absolute, month/date are 1-based, hour/minute/second are 0-based.
+static inline mp_timestamp_t timeutils_seconds_since_2000(mp_uint_t year, mp_uint_t month, mp_uint_t date,
+    mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
+    return (mp_timestamp_t)timeutils_seconds_since_1970(year, month, date, hour, minute, second) - TIMEUTILS_SECONDS_1970_TO_2000;
+}
+
+// Year is absolute, month/mday are 1-based, hours/minutes/seconds are 0-based.
+static inline mp_timestamp_t timeutils_mktime_2000(mp_uint_t year, mp_int_t month, mp_int_t mday,
+    mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
+    return (mp_timestamp_t)timeutils_mktime_1970(year, month, mday, hours, minutes, seconds) - TIMEUTILS_SECONDS_1970_TO_2000;
+}
+
+
 // Select the Epoch used by the port.
 #if MICROPY_EPOCH_IS_1970
 
-static inline void timeutils_seconds_since_epoch_to_struct_time(uint64_t t, timeutils_struct_time_t *tm) {
-    // TODO this will give incorrect results for dates before 2000/1/1
-    timeutils_seconds_since_2000_to_struct_time((mp_uint_t)(t - TIMEUTILS_SECONDS_1970_TO_2000), tm);
-}
-
-// Year is absolute, month/mday are 1-based, hours/minutes/seconds are 0-based.
-static inline uint64_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday, mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
-    return timeutils_mktime_2000(year, month, mday, hours, minutes, seconds) + TIMEUTILS_SECONDS_1970_TO_2000;
+static inline void timeutils_seconds_since_epoch_to_struct_time(mp_timestamp_t t, timeutils_struct_time_t *tm) {
+    timeutils_seconds_since_1970_to_struct_time(t, tm);
 }
 
 // Year is absolute, month/date are 1-based, hour/minute/second are 0-based.
-static inline uint64_t timeutils_seconds_since_epoch(mp_uint_t year, mp_uint_t month,
-    mp_uint_t date, mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
-    // TODO this will give incorrect results for dates before 2000/1/1
-    return timeutils_seconds_since_2000(year, month, date, hour, minute, second) + TIMEUTILS_SECONDS_1970_TO_2000;
+static inline mp_timestamp_t timeutils_seconds_since_epoch(mp_uint_t year, mp_uint_t month, mp_uint_t date,
+    mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
+    return timeutils_seconds_since_1970(year, month, date, hour, minute, second);
 }
 
-static inline mp_uint_t timeutils_seconds_since_epoch_from_nanoseconds_since_1970(uint64_t ns) {
-    return (mp_uint_t)(ns / 1000000000ULL);
+// Year is absolute, month/mday are 1-based, hours/minutes/seconds are 0-based.
+static inline mp_timestamp_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+    mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
+    return timeutils_mktime_1970(year, month, mday, hours, minutes, seconds);
 }
 
-static inline uint64_t timeutils_nanoseconds_since_epoch_to_nanoseconds_since_1970(uint64_t ns) {
+static inline mp_timestamp_t timeutils_seconds_since_epoch_from_nanoseconds_since_1970(int64_t ns) {
+    return (mp_timestamp_t)(ns / 1000000000LL);
+}
+
+static inline int64_t timeutils_seconds_since_epoch_to_nanoseconds_since_1970(mp_timestamp_t s) {
+    return (int64_t)s * 1000000000LL;
+}
+
+static inline int64_t timeutils_nanoseconds_since_epoch_to_nanoseconds_since_1970(int64_t ns) {
     return ns;
 }
 
 #else // Epoch is 2000
 
-#define timeutils_seconds_since_epoch_to_struct_time timeutils_seconds_since_2000_to_struct_time
-#define timeutils_seconds_since_epoch timeutils_seconds_since_2000
-#define timeutils_mktime timeutils_mktime_2000
-
-static inline uint64_t timeutils_seconds_since_epoch_to_nanoseconds_since_1970(mp_uint_t s) {
-    return ((uint64_t)s + TIMEUTILS_SECONDS_1970_TO_2000) * 1000000000ULL;
+static inline void timeutils_seconds_since_epoch_to_struct_time(mp_timestamp_t t, timeutils_struct_time_t *tm) {
+    timeutils_seconds_since_2000_to_struct_time(t, tm);
 }
 
-static inline mp_uint_t timeutils_seconds_since_epoch_from_nanoseconds_since_1970(uint64_t ns) {
-    return ns / 1000000000ULL - TIMEUTILS_SECONDS_1970_TO_2000;
+// Year is absolute, month/date are 1-based, hour/minute/second are 0-based.
+static inline mp_timestamp_t timeutils_seconds_since_epoch(mp_uint_t year, mp_uint_t month, mp_uint_t date,
+    mp_uint_t hour, mp_uint_t minute, mp_uint_t second) {
+    return timeutils_seconds_since_2000(year, month, date, hour, minute, second);
+}
+
+// Year is absolute, month/mday are 1-based, hours/minutes/seconds are 0-based.
+static inline mp_timestamp_t timeutils_mktime(mp_uint_t year, mp_int_t month, mp_int_t mday,
+    mp_int_t hours, mp_int_t minutes, mp_int_t seconds) {
+    return timeutils_mktime_2000(year, month, mday, hours, minutes, seconds);
+}
+
+static inline mp_timestamp_t timeutils_seconds_since_epoch_from_nanoseconds_since_1970(int64_t ns) {
+    return (mp_timestamp_t)(ns / 1000000000LL - TIMEUTILS_SECONDS_1970_TO_2000);
+}
+
+static inline int64_t timeutils_seconds_since_epoch_to_nanoseconds_since_1970(mp_timestamp_t s) {
+    return ((int64_t)s + TIMEUTILS_SECONDS_1970_TO_2000) * 1000000000LL;
 }
 
 static inline int64_t timeutils_nanoseconds_since_epoch_to_nanoseconds_since_1970(int64_t ns) {
-    return ns + TIMEUTILS_SECONDS_1970_TO_2000 * 1000000000ULL;
+    return ns + TIMEUTILS_SECONDS_1970_TO_2000 * 1000000000LL;
 }
 
 #endif
 
-int timeutils_calc_weekday(int y, int m, int d);
-
 #endif // MICROPY_INCLUDED_LIB_TIMEUTILS_TIMEUTILS_H

tests/extmod/time_mktime.py

@@ -0,0 +1,120 @@
+# test conversion from date tuple to timestamp and back
+
+try:
+    import time
+
+    time.localtime
+except (ImportError, AttributeError):
+    print("SKIP")
+    raise SystemExit
+
+# Range of date expected to work on all MicroPython platforms
+MIN_YEAR = 1970
+MAX_YEAR = 2099
+# CPython properly supported date range:
+# - on Windows: year 1970 to 3000+
+# - on Unix:    year 1583 to 3000+
+
+# Start test from Jan 1, 2001 13:00 (Feb 2000 might already be broken)
+SAFE_DATE = (2001, 1, 1, 13, 0, 0, 0, 0, -1)
+
+
+# mktime function that checks that the result is reversible
+def safe_mktime(date_tuple):
+    try:
+        res = time.mktime(date_tuple)
+        chk = time.localtime(res)
+    except OverflowError:
+        print("safe_mktime:", date_tuple, "overflow error")
+        return None
+    if chk[0:5] != date_tuple[0:5]:
+        print("safe_mktime:", date_tuple[0:5], " -> ", res, " -> ", chk[0:5])
+        return None
+    return res
+
+
+# localtime function that checks that the result is reversible
+def safe_localtime(timestamp):
+    try:
+        res = time.localtime(timestamp)
+        chk = time.mktime(res)
+    except OverflowError:
+        print("safe_localtime:", timestamp, "overflow error")
+        return None
+    if chk != timestamp:
+        print("safe_localtime:", timestamp, " -> ", res, " -> ", chk)
+        return None
+    return res
+
+
+# look for smallest valid timestamps by iterating backwards on tuple
+def test_bwd(date_tuple):
+    curr_stamp = safe_mktime(date_tuple)
+    year = date_tuple[0]
+    month = date_tuple[1] - 1
+    if month < 1:
+        year -= 1
+        month = 12
+    while year >= MIN_YEAR:
+        while month >= 1:
+            next_tuple = (year, month) + date_tuple[2:]
+            next_stamp = safe_mktime(next_tuple)
+            # at this stage, only test consistency and monotonicity
+            if next_stamp is None or next_stamp >= curr_stamp:
+                return date_tuple
+            date_tuple = next_tuple
+            curr_stamp = next_stamp
+            month -= 1
+        year -= 1
+        month = 12
+    return date_tuple
+
+
+# test day-by-day to ensure that every date is properly converted
+def test_fwd(start_date):
+    DAYS_PER_MONTH = (0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
+    curr_stamp = safe_mktime(start_date)
+    curr_date = safe_localtime(curr_stamp)
+    while curr_date[0] <= MAX_YEAR:
+        if curr_date[2] < 15:
+            skip_days = 13
+        else:
+            skip_days = 1
+        next_stamp = curr_stamp + skip_days * 86400
+        next_date = safe_localtime(next_stamp)
+        if next_date is None:
+            return curr_date
+        if next_date[2] != curr_date[2] + skip_days:
+            # next month
+            if next_date[2] != 1:
+                print("wrong day of month:", next_date)
+                return curr_date
+            # check the number of days in previous month
+            month_days = DAYS_PER_MONTH[curr_date[1]]
+            if month_days == 28 and curr_date[0] % 4 == 0:
+                if curr_date[0] % 100 != 0 or curr_date[0] % 400 == 0:
+                    month_days += 1
+            if curr_date[2] != month_days:
+                print("wrong day count in prev month:", curr_date[2], "vs", month_days)
+                return curr_date
+            if next_date[1] != curr_date[1] + 1:
+                # next year
+                if curr_date[1] != 12:
+                    print("wrong month count in prev year:", curr_date[1])
+                    return curr_date
+                if next_date[1] != 1:
+                    print("wrong month:", next_date)
+                    return curr_date
+                if next_date[0] != curr_date[0] + 1:
+                    print("wrong year:", next_date)
+                    return curr_date
+        curr_stamp = next_stamp
+        curr_date = next_date
+    return curr_date
+
+
+small_date = test_bwd(SAFE_DATE)
+large_date = test_fwd(small_date)
+print("tested from", small_date[0:3], "to", large_date[0:3])
+print(small_date[0:3], "wday is", small_date[6])
+print(large_date[0:3], "wday is", large_date[6])