diff --git a/Libraries/LibCore/DateTime.cpp b/Libraries/LibCore/DateTime.cpp
index 1836c2d6a7..dac7c97599 100644
--- a/Libraries/LibCore/DateTime.cpp
+++ b/Libraries/LibCore/DateTime.cpp
@@ -36,6 +36,22 @@ DateTime DateTime::now()
     return from_timestamp(time(nullptr));
 }
 
+DateTime DateTime::create(unsigned year, unsigned month, unsigned day, unsigned hour, unsigned minute, unsigned second)
+{
+    DateTime dt;
+    dt.m_year = year;
+    dt.m_month = month;
+    dt.m_day = day;
+    dt.m_hour = hour;
+    dt.m_minute = minute;
+    dt.m_second = second;
+
+    struct tm tm = { (int)second, (int)minute, (int)hour, (int)day, (int)month, (int)year, (int)dt.weekday(), (int)dt.day_of_year(), -1 };
+    dt.m_timestamp = mktime(&tm);
+
+    return dt;
+}
+
 DateTime DateTime::from_timestamp(time_t timestamp)
 {
     struct tm tm;
@@ -51,6 +67,55 @@ DateTime DateTime::from_timestamp(time_t timestamp)
     return dt;
 }
 
+unsigned DateTime::weekday() const
+{
+    int target_year = m_year;
+    static const int seek_table[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
+    if (m_month < 3)
+        --target_year;
+
+    return (target_year + target_year / 4 - target_year / 100 + target_year / 400 + seek_table[m_month - 1] + m_day) % 7;
+}
+
+unsigned DateTime::days_in_month() const
+{
+    bool is_long_month = (m_month == 1 || m_month == 3 || m_month == 5 || m_month == 7 || m_month == 8 || m_month == 10 || m_month == 12);
+
+    if (m_month == 2)
+        return is_leap_year() ? 29 : 28;
+
+    return is_long_month ? 31 : 30;
+}
+
+unsigned DateTime::day_of_year() const
+{
+    static const int seek_table[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
+    int day_of_year = seek_table[m_month - 1] + m_day;
+
+    if (is_leap_year() && m_month > 3)
+        day_of_year++;
+
+    return day_of_year - 1;
+}
+
+bool DateTime::is_leap_year() const
+{
+    return ((m_year % 400 == 0) || (m_year % 4 == 0 && m_year % 100 != 0));
+}
+
+void DateTime::set_time(unsigned year, unsigned month, unsigned day, unsigned hour, unsigned minute, unsigned second)
+{
+    m_year = year;
+    m_month = month;
+    m_day = day;
+    m_hour = hour;
+    m_minute = minute;
+    m_second = second;
+
+    struct tm tm = { (int)second, (int)minute, (int)hour, (int)day, (int)month, (int)year, (int)weekday(), (int)day_of_year(), -1 };
+    m_timestamp = mktime(&tm);
+}
+
 String DateTime::to_string(const String& format) const
 {
 
diff --git a/Libraries/LibCore/DateTime.h b/Libraries/LibCore/DateTime.h
index 56a9b17680..4409b42b07 100644
--- a/Libraries/LibCore/DateTime.h
+++ b/Libraries/LibCore/DateTime.h
@@ -42,9 +42,15 @@ public:
     unsigned hour() const { return m_hour; }
     unsigned minute() const { return m_minute; }
     unsigned second() const { return m_second; }
+    unsigned weekday() const;
+    unsigned days_in_month() const;
+    unsigned day_of_year() const;
+    bool is_leap_year() const;
 
+    void set_time(unsigned year, unsigned month = 1, unsigned day = 0, unsigned hour = 0, unsigned minute = 0, unsigned second = 0);
     String to_string(const String& format = "%Y-%m-%d %H:%M:%S") const;
 
+    static DateTime create(unsigned year, unsigned month = 1, unsigned day = 0, unsigned hour = 0, unsigned minute = 0, unsigned second = 0);
     static DateTime now();
     static DateTime from_timestamp(time_t);
 
diff --git a/Userland/cal.cpp b/Userland/cal.cpp
index 8329645a10..4f14a33ba6 100644
--- a/Userland/cal.cpp
+++ b/Userland/cal.cpp
@@ -25,6 +25,7 @@
  */
 
 #include <LibCore/ArgsParser.h>
+#include <LibCore/DateTime.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
@@ -43,26 +44,6 @@ int target_day;
 int current_year;
 int current_month;
 
-int day_of_week(int day, int month, int year)
-{
-    static const int seek_table[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
-    if (month < 3)
-        --year;
-
-    return (year + year / 4 - year / 100 + year / 400 + seek_table[month - 1] + day) % 7;
-}
-
-int get_number_of_days(int month, int year)
-{
-    bool is_leap_year = ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0));
-    bool is_long_month = (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12);
-
-    if (month == 2)
-        return is_leap_year ? 29 : 28;
-
-    return is_long_month ? 31 : 30;
-}
-
 void append_to_print(char* buffer, int row, int column, char* text)
 {
     int starting_point = (line_width * row) + (column * column_width);
@@ -84,10 +65,10 @@ void insert_month_to_print(int column, int month, int year)
     sprintf(temp_buffer, "Su Mo Tu We Th Fr Sa");
     append_to_print(print_buffer, printing_row, printing_column, temp_buffer);
     printing_row++;
-
     int day_to_print = 1;
-    int first_day_of_week_for_month = day_of_week(1, month, year);
-    int days_in_the_month = get_number_of_days(month, year);
+    auto date_time = Core::DateTime::create(year, month, 1);
+    int first_day_of_week_for_month = date_time.weekday();
+    int days_in_the_month = date_time.days_in_month();
     int last_written_chars = 0;
     for (int i = 1; day_to_print <= days_in_the_month; ++i) {
         if (i - 1 < first_day_of_week_for_month) {