diff --git a/addons/common/CfgFunctions.hpp b/addons/common/CfgFunctions.hpp
index 794c76817..118b7ed60 100644
--- a/addons/common/CfgFunctions.hpp
+++ b/addons/common/CfgFunctions.hpp
@@ -114,6 +114,10 @@ class CfgFunctions {
             PATHTO_FNC(getNearestBuilding);
         };
 
+        class DateTime {
+            PATHTO_FNC(weekDay);
+        };
+
         class Misc {
             PATHTO_FNC(addPerFrameHandler);
             PATHTO_FNC(removePerFrameHandler);
diff --git a/addons/common/fnc_weekDay.sqf b/addons/common/fnc_weekDay.sqf
new file mode 100644
index 000000000..5f7552838
--- /dev/null
+++ b/addons/common/fnc_weekDay.sqf
@@ -0,0 +1,36 @@
+#include "script_component.hpp"
+/* ----------------------------------------------------------------------------
+Function: CBA_fnc_weekDay
+
+Description:
+    Calculates date's day of the week using a modified Rata Die method with fractional years.
+
+Parameters:
+    _date - Date of [year, month, day]. <ARRAY>
+
+Returns:
+    Day of the week (0: Sunday, 6: Saturday, -1: invalid) <NUMBER>
+
+Examples:
+    (begin example)
+        [systemTimeUTC] call CBA_fnc_weekDay;
+        [date] call CBA_fnc_weekDay;
+        [[2022, 2, 16]] call CBA_fnc_weekDay;
+    (end)
+
+Author:
+    Jonpas
+---------------------------------------------------------------------------- */
+
+params [["_date", [0, 0, 0], [[]], [3, 4, 5, 6, 7]]];
+
+// Keep only year, month, day if longer date format is given
+// Hours and minutes must be given as 0 for dateToNumber to work correctly for this use-case
+_date = [_date select 0, _date select 1, _date select 2, 0, 0];
+
+private _yearBefore = ((_date select 0) - 1) max 0;
+private _leapYears = floor (_yearBefore / 4);
+private _normalYears = _yearBefore - _leapYears;
+private _days = _normalYears + (_leapYears * (366 / 365)) + dateToNumber _date;
+
+(round (_days / (1 / 365))) mod 7 // return
diff --git a/addons/common/test.sqf b/addons/common/test.sqf
index 63e8537e3..b3dea79de 100644
--- a/addons/common/test.sqf
+++ b/addons/common/test.sqf
@@ -5,7 +5,7 @@
 #define DEBUG_MODE_FULL
 #include "script_component.hpp"
 
-#define TESTS ["config", "inventory", "weaponComponents", "position", "ret", "macro_is_x"]
+#define TESTS ["common", "config", "inventory", "weaponComponents", "position", "ret", "macro_is_x"]
 
 SCRIPT(test-common);
 
diff --git a/addons/common/test_common.sqf b/addons/common/test_common.sqf
new file mode 100644
index 000000000..8f5235a74
--- /dev/null
+++ b/addons/common/test_common.sqf
@@ -0,0 +1,33 @@
+#include "script_component.hpp"
+SCRIPT(test_common);
+
+// execVM "\x\cba\addons\common\test_common.sqf";
+
+private ["_funcName", "_result"];
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+_funcName = "CBA_fnc_weekDay";
+LOG("Testing " + _funcName);
+
+TEST_DEFINED("CBA_fnc_weekDay","");
+
+_result = [] call CBA_fnc_weekDay;
+TEST_TRUE(_result == -1,_funcName); // invalid
+
+_result = [[0, 0, 0]] call CBA_fnc_weekDay;
+TEST_TRUE(_result == -1,_funcName); // invalid
+
+_result = [[2022, 1, 1]] call CBA_fnc_weekDay;
+TEST_TRUE(_result == 6,_funcName); // Saturday
+
+_result = [[2022, 2, 16]] call CBA_fnc_weekDay;
+TEST_TRUE(_result == 3,_funcName); // Wednesday
+
+// date format [year, month, day, hour, minute]
+_result = [[2022, 2, 17, 11, 56]] call CBA_fnc_weekDay;
+TEST_TRUE(_result == 4,_funcName); // Thursday
+
+// systemTime format [year, month, day, hour, minute, second, millisecond]
+_result = [[2022, 2, 18, 11, 56, 24, 126]] call CBA_fnc_weekDay;
+TEST_TRUE(_result == 5,_funcName); // Friday