MomentJS style .NET DateTime extensions

DateTimeExtensions.cs

public static class DateTimeExtensions {
    #region Day

    public static DateTime StartOfDay(this DateTime d) {
        return d.Date;
    }

    public static DateTime EndOfDay(this DateTime d) {
        return new DateTime(d.Year, d.Month, d.Day, 23, 59, 59);
    }

    #endregion

    #region Week

    public static DateTime AddWeeks(this DateTime d, double weeks) {
        return d.AddDays(weeks * 7);
    }

    public static DateTime StartOfWeek(this DateTime d) {
        return d.AddDays(0 - (int)d.DayOfWeek).Date;
    }

    public static DateTime EndOfWeek(this DateTime d) {
        return d.AddDays(6 - ((int)d.DayOfWeek)).Date;
    }

    #endregion

    #region Month

    public static DateTime StartOfMonth(this DateTime d) {
        return new DateTime(d.Year, d.Month, 1).Date;
    }

    public static DateTime EndOfMonth(this DateTime d) {
        return new DateTime(d.Year, d.Month, CultureInfo.CurrentCulture.Calendar.GetDaysInMonth(d.Year, d.Month)).Date;
    }

    #endregion

    #region IsSame

    /// <summary>
    ///     Compares the two given DateTimes based on the given
    ///     comparison.
    /// 
    ///     The comparison also checks each "higher level" property.
    ///     For example if you are using <code>DateTimeComparison.Month</code>
    ///     the year will also be compared.
    /// </summary>
    public static bool IsSame(this DateTime a, DateTime b, DateTimeComparison comparison) {

        if (a.Year != b.Year) return false;
        if (comparison == DateTimeComparison.Year) return true;

        if (a.Month != b.Month) return false;
        if (comparison == DateTimeComparison.Month) return true;

        if (a.Day != b.Day) return false;
        if (comparison == DateTimeComparison.Day) return true;

        if (a.Hour != b.Hour) return false;
        if (comparison == DateTimeComparison.Hour) return true;

        if (a.Minute != b.Minute) return false;
        if (comparison == DateTimeComparison.Minute) return true;

        return a.Second == b.Second;
    }

    #endregion

    #region IsCurrent

    /// <summary>
    ///     Compares the given <see cref="DateTime"/> to the current date and
    ///		time based on the given comparison.
    /// 
    ///     The comparison also checks each "higher level" property.
    ///     For example if you are using <code>DateTimeComparison.Month</code>
    ///     the year will also be compared.
    /// </summary>
    public static bool IsCurrent(this DateTime a, DateTimeComparison comparison) {
        return IsSame(a, DateTime.Now, comparison);
    }

    #endregion

    #region IsTomorrow

    /// <summary>
    ///     Determines whether the given DateTime represents
    ///     the day after the current date (using <c>DateTime.Today</c>).
    /// </summary>
    public static bool IsTomorrow(this DateTime a) {
        return IsSame(a, DateTime.Today.AddDays(1.0), DateTimeComparison.Day);
    }

    #endregion

    #region IsYesterday

    /// <summary>
    ///     Determines whether the given DateTime represents
    ///     the day before the current date (using <c>DateTime.Today</c>).
    /// </summary>
    public static bool IsYesterday(this DateTime a) {
        return IsSame(a, DateTime.Today.AddDays(-1.0), DateTimeComparison.Day);
    }

    #endregion

    #region IsBefore

    /// <summary>
    ///     Returns true if the current <see cref="DateTime"/> represents
    ///     a point in time that occurs BEFORE the point in time represented
    ///     by <paramref name="b"/>.
    /// 
    ///     The comparison also checks each "higher level" property.
    ///     For example if you are using <code>DateTimeComparison.Month</code>
    ///     the year will also be compared.
    /// </summary>
    public static bool IsBefore(this DateTime a, DateTime b, DateTimeComparison comparison) {

        if (a.Year < b.Year) return true;
        if (a.Year > b.Year || comparison == DateTimeComparison.Year) return false;
        
        if (a.Month < b.Month) return true;
        if (a.Month > b.Month || comparison == DateTimeComparison.Month) return false;

        if (a.Day < b.Day) return true;
        if (a.Day > b.Day || comparison == DateTimeComparison.Day) return false;

        if (a.Hour < b.Hour) return true;
        if (a.Hour > b.Hour || comparison == DateTimeComparison.Hour) return false;

        if (a.Minute < b.Minute) return true;
        if (a.Minute > b.Minute || comparison == DateTimeComparison.Minute) return false;
        
        return a.Second < b.Second;
    }

    #endregion

    #region IsAfter

    /// <summary>
    ///     Returns true if the current <see cref="DateTime"/> represents
    ///     a point in time that occurs AFTER the point in time represented
    ///     by <paramref name="b"/>.
    /// 
    ///     The comparison also checks each "higher level" property.
    ///     For example if you are using <code>DateTimeComparison.Month</code>
    ///     the year will also be compared.
    /// </summary>
    public static bool IsAfter(this DateTime a, DateTime b, DateTimeComparison comparison) {

        if (a.Year > b.Year) return true;
        if (a.Year < b.Year || comparison == DateTimeComparison.Year) return false;

        if (a.Month > b.Month) return true;
        if (a.Month < b.Month || comparison == DateTimeComparison.Month) return false;

        if (a.Day > b.Day) return true;
        if (a.Day < b.Day || comparison == DateTimeComparison.Day) return false;

        if (a.Hour > b.Hour) return true;
        if (a.Hour < b.Hour || comparison == DateTimeComparison.Hour) return false;

        if (a.Minute > b.Minute) return true;
        if (a.Minute < b.Minute || comparison == DateTimeComparison.Minute) return false;

        return a.Second > b.Second;
    }

    #endregion

    #region IsBetween

    public static bool IsBetween(this DateTime a, DateTime startDate, DateTime endDate, DateTimeComparison comparison) {

		double startDiff = (a - startDate).TotalSeconds;
        double endDiff = (endDate - a).TotalSeconds;

        if (comparison == DateTimeComparison.Second) {
	        return 0 <= startDiff && 0 <= endDiff;
        }

		// Minute
        startDiff = Math.Round(startDiff/60);
        endDiff = Math.Round(endDiff/60);

		if (comparison == DateTimeComparison.Minute) {
			return 0 <= startDiff && 0 <= endDiff;
		}

		// Hour
		startDiff = Math.Round(startDiff / 60);
		endDiff = Math.Round(endDiff / 60);

		if (comparison == DateTimeComparison.Hour) {
			return 0 <= startDiff && 0 <= endDiff;
		}

		// Day
		startDiff = Math.Round(startDiff / 24);
		endDiff = Math.Round(endDiff / 24);

		if (comparison == DateTimeComparison.Day) {
			return 0 <= startDiff && 0 <= endDiff;
		}

		throw new NotSupportedException("Cannot diff DateTimeComparison.Month or DateTimeComparison.Year");
    }

    #endregion
}

public enum DateTimeComparison {
    Year,
    Month,
    Day,
    Hour,
    Minute,
    Second
}

public static class TimeSpanExtensions {
    /// <summary>
    ///     Converts the given TimeSpan to a date time
    ///     using the Unix epoch for the year, month and day.
    /// </summary>
    public static DateTime ToDateTime(this TimeSpan ts) {
        return ts.ToDateTime(new DateTime(1970, 1, 1));
    }

    /// <summary>
    ///     Converts the given TimeSpan to a date time
    ///     using the given DateTime for the year, month and day.
    /// </summary>
    public static DateTime ToDateTime(this TimeSpan ts, DateTime d) {
        if (ts.TotalDays >= 1) {
            throw new ArgumentOutOfRangeException("ts", "The given TimeSpan cannot represent a duration greater than a day.");
        }

        return DateTimeHelper.FromDateAndTime(d, ts);
    }
}

public static class DateTimeHelper {
    /// <summary>
    ///     Creates a new date using the given <paramref name="date"/>
    ///     for the date (ie. a day) and the given <paramref name="time"/>
    ///     as the time (eg. 09:00).
    /// </summary>
    /// <param name="d">The date.</param>
    /// <param name="ts">The time.</param>
    /// <returns>A newly formed date time.</returns>
    public static DateTime FromDateAndTime(DateTime d, TimeSpan ts) {
        return new DateTime(d.Year, d.Month, d.Day, ts.Hours, ts.Minutes, ts.Seconds);
    }
}