Added LocalClock.

README.md

@@ -1,9 +1,11 @@
 # libcron
 A C++ scheduling library using cron formatting.
 
-# Time zones
+# Local time vs UTC
 
-This library uses `std::chrono::system_clock::timepoint` as its time unit, thus all calculations are in UTC. 
+This library uses `std::chrono::system_clock::timepoint` as its time unit. While that is UTC by default, the Cron-class
+uses a `LocalClock` by default which offsets `system_clock::now()` by the current UTC-offset. If you wish to work in
+UTC, then construct the Cron instance, passing it a `libcron::UTCClock`.  
 
 # Supported formatting
 
@@ -67,5 +69,5 @@ the '?'-character unless one field already is something other than '*'.
 
 # Third party libraries
 
-Howard Hinnant's [date.h](https://github.com/HowardHinnant/date/)
+Howard Hinnant's [date libraries](https://github.com/HowardHinnant/date/)
 

libcron/Cron.h

@@ -13,7 +13,7 @@ namespace libcron
     {
         public:
 
-            explicit Cron(std::unique_ptr<ICronClock> clock = std::make_unique<UTCClock>())
+            explicit Cron(std::unique_ptr<ICronClock> clock = std::make_unique<LocalClock>())
                     : clock(std::move(clock))
             {
             }

libcron/CronClock.h

@@ -2,12 +2,16 @@
 
 #include <chrono>
 
+using namespace std::chrono;
+using namespace date;
+
 namespace libcron
 {
     class ICronClock
     {
         public:
             virtual std::chrono::system_clock::time_point now() = 0;
+            virtual std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) = 0;
     };
 
     class UTCClock
@@ -18,5 +22,33 @@ namespace libcron
             {
                 return std::chrono::system_clock::now();
             }
+
+            std::chrono::seconds utc_offset(std::chrono::system_clock::time_point) override
+            {
+                return 0s;
+            }
+    };
+
+    class LocalClock
+            : public ICronClock
+    {
+        public:
+            std::chrono::system_clock::time_point now() override
+            {
+                auto now = system_clock::now();
+                return now + utc_offset(now);
+            }
+
+            std::chrono::seconds utc_offset(std::chrono::system_clock::time_point now) override
+            {
+                auto t = system_clock::to_time_t(now);
+                tm tm{};
+#ifdef __WIN32
+                localtime_s(&tm, &t);
+#else
+                localtime_r(&t, &tm);
+#endif
+                return seconds{tm.tm_gmtoff};
+            }
     };
 }

test/CronScheduleTest.cpp

@@ -16,7 +16,7 @@ system_clock::time_point DT(year_month_day ymd, hours h = hours{0}, minutes m =
 }
 
 bool test(const std::string& schedule, system_clock::time_point from,
-          std::vector<system_clock::time_point> expected_next)
+          const std::vector<system_clock::time_point>& expected_next)
 {
     auto c = CronData::create(schedule);
     bool res = c.is_valid();
@@ -209,22 +209,6 @@ SCENARIO("Examples from README.md")
                  }));
 }
 
-//SCENARIO("Daylight Savings Time")
-//{
-//    // In sweden when local standard time is about to reach
-//    //Sunday, 25 March 2018, 02:00:00 clocks are turned forward 1 hour to
-//    //Sunday, 25 March 2018, 03:00:00 local daylight time instead.
-//
-//    REQUIRE(test("0 0 * * * ?", DT(2018_y / 3 / 25, hours{0}),
-//                 {
-//                         DT(2018_y / 3 / 25, hours{0}),
-//                         DT(2018_y / 3 / 25, hours{1}),
-//                         // This hour disappear! DT(2018_y / 3 / 25, hours{2}),
-//                         DT(2018_y / 3 / 25, hours{3}),
-//                         DT(2018_y / 3 / 25, hours{4})
-//                 }));
-//}
-
 SCENARIO("Unable to calculate time point")
 {
     // TODO: Find a schedule that is unsolvable.

test/CronTest.cpp

@@ -6,9 +6,9 @@
 using namespace libcron;
 using namespace std::chrono;
 
-std::string create_schedule_expiring_in(hours h, minutes m, seconds s)
+std::string create_schedule_expiring_in(std::shared_ptr<ICronClock> clock, hours h, minutes m, seconds s)
 {
-    auto now = system_clock::now() + h + m + s;
+    auto now = clock->now() + h + m + s;
     auto dt = CronSchedule::to_calendar_time(now);
 
     std::string res{};
@@ -66,7 +66,7 @@ SCENARIO("Adding a task that expires in the future")
         auto expired = false;
 
         Cron c;
-        REQUIRE(c.add_schedule("A task", create_schedule_expiring_in(hours{0}, minutes{0}, seconds{3}),
+        REQUIRE(c.add_schedule("A task", create_schedule_expiring_in(c.get_clock(), hours{0}, minutes{0}, seconds{3}),
                                [&expired]()
                                {
                                    expired = true;
@@ -107,14 +107,14 @@ SCENARIO("Task priority")
 
 
         Cron c;
-        REQUIRE(c.add_schedule("Five", create_schedule_expiring_in(hours{0}, minutes{0}, seconds{5}),
+        REQUIRE(c.add_schedule("Five", create_schedule_expiring_in(c.get_clock(), hours{0}, minutes{0}, seconds{5}),
                                [&_5_second_expired]()
                                {
                                    _5_second_expired++;
                                })
         );
 
-        REQUIRE(c.add_schedule("Three", create_schedule_expiring_in(hours{0}, minutes{0}, seconds{3}),
+        REQUIRE(c.add_schedule("Three", create_schedule_expiring_in(c.get_clock(), hours{0}, minutes{0}, seconds{3}),
                                [&_3_second_expired]()
                                {
                                    _3_second_expired++;