public static int TotalDaysBetween(DateTime time1, DateTime time2) =>
 DateTimeSpan.CompareDates(time1, time2).Days;
 public static int TotalHoursBetween(DateTime time1, DateTime time2) =>
 DateTimeSpan.CompareDates(time1, time2).Hours;
 public static int TotalMonthsBetween(DateTime time1, DateTime time2) =>
 DateTimeSpan.CompareDates(time1, time2).Months +
 DateTimeSpan.CompareDates(time1, time2).Years * 12;
        public static DateTimeSpan CompareDates(DateTime date1, DateTime date2)
        {
            if (date2 < date1)
            {
                var sub = date1;
                date1 = date2;
                date2 = sub;
            }

            DateTime current = date1;
            int      years   = 0;
            int      months  = 0;
            int      days    = 0;

            Phase        phase       = Phase.Years;
            DateTimeSpan span        = new DateTimeSpan();
            int          officialDay = current.Day;

            while (phase != Phase.Done)
            {
                switch (phase)
                {
                case Phase.Years:
                    if (current.AddYears(years + 1) > date2)
                    {
                        phase   = Phase.Months;
                        current = current.AddYears(years);
                    }
                    else
                    {
                        years++;
                    }

                    break;

                case Phase.Months:
                    if (current.AddMonths(months + 1) > date2)
                    {
                        phase   = Phase.Days;
                        current = current.AddMonths(months);
                        if (current.Day < officialDay &&
                            officialDay <= DateTime.DaysInMonth(current.Year, current.Month))
                        {
                            current = current.AddDays(officialDay - current.Day);
                        }
                    }
                    else
                    {
                        months++;
                    }

                    break;

                case Phase.Days:
                    if (current.AddDays(days + 1) > date2)
                    {
                        current = current.AddDays(days);
                        var timespan = date2 - current;
                        span = new DateTimeSpan(years, months, days, timespan.Hours, timespan.Minutes,
                                                timespan.Seconds, timespan.Milliseconds);
                        phase = Phase.Done;
                    }
                    else
                    {
                        days++;
                    }

                    break;
                }
            }

            return(span);
        }
 public static int TotalWeeksBetween(DateTime time1, DateTime time2) =>
 (int)Math.Ceiling(DateTimeSpan.CompareDates(time1, time2).Days / 7d);
 public static int TotalMillisecondsBetween(DateTime time1, DateTime time2) =>
 DateTimeSpan.CompareDates(time1, time2).Milliseconds;
 public static int TotalMinutesBetween(DateTime time1, DateTime time2) =>
 DateTimeSpan.CompareDates(time1, time2).Minutes;