diff --git a/libc/src/time/mktime.cpp b/libc/src/time/mktime.cpp
--- a/libc/src/time/mktime.cpp
+++ b/libc/src/time/mktime.cpp
@@ -11,7 +11,6 @@
 
 namespace __llvm_libc {
 
-namespace {
 constexpr int SecondsPerMin = 60;
 constexpr int MinutesPerHour = 60;
 constexpr int HoursPerDay = 24;
@@ -27,26 +26,13 @@
 // susceptible to the Year 2038 problem.
 constexpr int EndOf32BitEpochYear = 2038;
 
-constexpr int LeapYearDaysInMonth[] = {
-  31 /* Jan */, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
-};
-
 constexpr int NonLeapYearDaysInMonth[] = {
   31 /* Jan */, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 };
 
-constexpr int LeapYearDaysByMonth[] = {
-  0 /* Jan */, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335
-};
-
-constexpr int NonLeapYearDaysByMonth[] = {
-  0 /* Jan */, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
-};
-
 constexpr bool isLeapYear (const time_t year) {
   return (((year) % 4) == 0 && (((year) % 100) != 0 || ((year) % 400) == 0));
 }
-}
 
 time_t LLVM_LIBC_ENTRYPOINT(mktime)(struct tm *t1) {
   // Unlike most C Library functions, mktime doesn't just die on bad input.
@@ -79,22 +65,25 @@
   }
 
   static_assert(sizeof(int) == 4,
-                "ILP64 is uimplemented.  Ths implementation requires 32-bit "
-                "integers.");
+                "ILP64 is unimplemented.  This implementation requires "
+                "32-bit integers.");
 
   if (t1->tm_mon < 0 || t1->tm_mon > (MonthsPerYear - 1))
     return (time_t)(-1);
   bool tmYearIsLeap = isLeapYear(tmYearFromBase);
-  time_t daysInMonth = tmYearIsLeap
-                       ? LeapYearDaysInMonth[t1->tm_mon]
-                       : NonLeapYearDaysInMonth[t1->tm_mon];
+  time_t daysInMonth = NonLeapYearDaysInMonth[t1->tm_mon];
+  // Add one day if it is a leap year and the month is February.
+  if (tmYearIsLeap && t1->tm_mon == 1)
+    ++daysInMonth;
   if (t1->tm_mday < 1 || t1->tm_mday > daysInMonth)
     return (time_t)(-1);
 
   time_t totalDays = t1->tm_mday - 1;
-  totalDays += (tmYearIsLeap
-                ? LeapYearDaysByMonth[t1->tm_mon]
-                : NonLeapYearDaysByMonth[t1->tm_mon]);
+  for (int i = 0; i < t1->tm_mon; ++i)
+    totalDays += NonLeapYearDaysInMonth[i];
+  // Add one day if it is a leap year and the month is after February.
+  if (tmYearIsLeap && t1->tm_mon > 1)
+    totalDays++;
   t1->tm_yday = totalDays;
   totalDays += (tmYearFromBase - EpochYear) * DaysPerNonLeapYear;
 
@@ -111,7 +100,7 @@
   t1->tm_wday = (EpochWeekDay + totalDays) % DaysPerWeek;
   if (t1->tm_wday < 0)
     t1->tm_wday += DaysPerWeek;
-  // TODO(rtenneti): Need to handle timezone
+  // TODO(rtenneti): Need to handle timezone and update of tm_isdst.
   return t1->tm_sec
       + t1->tm_min * SecondsPerMin
       + t1->tm_hour * MinutesPerHour * SecondsPerMin