date.h as git submodule.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "libcron/externals/date"]
+	path = libcron/externals/date
+	url = https://github.com/HowardHinnant/date.git

libcron/CMakeLists.txt

@@ -4,7 +4,7 @@ project(libcron)
 set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wpedantic")
 
-include_directories(externals/date)
+include_directories(${CMAKE_CURRENT_LIST_DIR}/externals/date/include)
 
 add_library(${PROJECT_NAME}
         Cron.h
@@ -15,6 +15,6 @@ add_library(${PROJECT_NAME}
         CronData.cpp
         CronSchedule.cpp
         CronSchedule.h
-        externals/date/date.h
         DateTime.h
-        Task.cpp CronClock.h)
+        Task.cpp
+        CronClock.h)

libcron/CronData.cpp

@@ -1,4 +1,4 @@
-#include <date.h>
+#include <date/date.h>
 #include "CronData.h"
 
 using namespace date;

libcron/CronSchedule.h

@@ -2,7 +2,7 @@
 
 #include "CronData.h"
 #include <chrono>
-#include "externals/date/date.h"
+#include <date/date.h>
 #include "DateTime.h"
 
 namespace libcron

test/CMakeLists.txt

@@ -5,9 +5,9 @@ set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wpedantic -Wextra")
 
 include_directories(
-        externals/Catch2/single_include/
-        ..
-        ../libcron/externals/date
+        ${CMAKE_CURRENT_LIST_DIR}/externals/Catch2/single_include/
+        ${CMAKE_CURRENT_LIST_DIR}/../libcron/externals/date/include
+        ${CMAKE_CURRENT_LIST_DIR}/..
 )
 
 add_executable(

test/CronDataTest.cpp

@@ -1,7 +1,7 @@
 #define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
 
 #include <catch.hpp>
-#include <date.h>
+#include <date/date.h>
 #include <libcron/Cron.h>
 #include <libcron/CronData.h>
 
@@ -21,8 +21,6 @@ bool has_value_range(const std::set<T>& set, uint8_t low, uint8_t high)
     return found;
 }
 
-
-
 SCENARIO("Numerical inputs")
 {
     GIVEN("Valid numerical inputs")

test/CronScheduleTest.cpp

@@ -1,6 +1,6 @@
 #include <catch.hpp>
 #include <chrono>
-#include <date.h>
+#include <date/date.h>
 #include <libcron/Cron.h>
 #include <iostream>