change year base for RTC time_t to correct leap processing

shellixyz · Jun 1, 2018 · 947eb3f · 947eb3f
1 parent e45cf00
commit 947eb3f
Showing 1 changed file with 10 additions and 6 deletions.
diff --git a/src/main/common/time.c b/src/main/common/time.c
@@ -32,7 +32,11 @@
 
 #include "drivers/time.h"
 
-#define UNIX_REFERENCE_YEAR 1970
+// For the "modulo 4" arithmetic to work, we need a leap base year
+#define REFERENCE_YEAR 2000
+// Offset (seconds) from the UNIX epoch (1970-01-01) to 2000-01-01
+#define EPOCH_2000_OFFSET 946684800
+
 #define MILLIS_PER_SECOND 1000
 
 // rtcTime_t when the system was started.
@@ -61,14 +65,14 @@ static rtcTime_t dateTimeToRtcTime(dateTime_t *dt)
  unsigned int hour = dt->hours; // 0-23
  unsigned int day = dt->day - 1; // 0-30
  unsigned int month = dt->month - 1; // 0-11
- unsigned int year = dt->year - UNIX_REFERENCE_YEAR; // 0-99
- int32_t unixTime = (((year / 4 * (365 * 4 + 1) + days[year % 4][month] + day) * 24 + hour) * 60 + minute) * 60 + second;
+ unsigned int year = dt->year - REFERENCE_YEAR; // 0-99
+ int32_t unixTime = (((year / 4 * (365 * 4 + 1) + days[year % 4][month] + day) * 24 + hour) * 60 + minute) * 60 + second + EPOCH_2000_OFFSET;
  return rtcTimeMake(unixTime, dt->millis);
 }
 
 static void rtcTimeToDateTime(dateTime_t *dt, rtcTime_t t)
 {
- int32_t unixTime = t / MILLIS_PER_SECOND;
+ int32_t unixTime = t / MILLIS_PER_SECOND - EPOCH_2000_OFFSET;
  dt->seconds = unixTime % 60;
  unixTime /= 60;
  dt->minutes = unixTime % 60;
@@ -93,7 +97,7 @@ static void rtcTimeToDateTime(dateTime_t *dt, rtcTime_t t)
  }
  }
 
- dt->year = years + year + UNIX_REFERENCE_YEAR;
+ dt->year = years + year + REFERENCE_YEAR;
  dt->month = month + 1;
  dt->day = unixTime - days[year][month] + 1;
  dt->millis = t % MILLIS_PER_SECOND;
@@ -112,7 +116,7 @@ static void rtcGetDefaultDateTime(dateTime_t *dateTime)
 
 static bool rtcIsDateTimeValid(dateTime_t *dateTime)
 {
- return (dateTime->year >= UNIX_REFERENCE_YEAR) &&
+ return (dateTime->year >= REFERENCE_YEAR) &&
  (dateTime->month >= 1 && dateTime->month <= 12) &&
  (dateTime->day >= 1 && dateTime->day <= 31) &&
  (dateTime->hours <= 23) &&