A switch case statement that returns a timespan

I have a switch case statement containing enum values as cases. These enum values are time units. Now I want to generate a timespan by using an enum value and a long value so like this:

2 (long) Minutes (Enum value)

1 (long) Year (Enum value)

... and so on.

This is the switch-case statement:

private const double yearValue = 365.2425;

public TimeSpan ResetTimeSpan
            {
                get
                {
                    switch (ResetTimeUnitEnumValue)
                    {
                        case TimeUnit.Seconds:
                            return new TimeSpan(0,0,0, (int)ResetTime);
                        case TimeUnit.Minutes:
                            return new TimeSpan(0, 0, (int)ResetTime, 0);
                        case TimeUnit.Hours:
                            return new TimeSpan(0, (int)ResetTime, 0);
                        case TimeUnit.Days:
                            return new TimeSpan((int)ResetTime, 0, 0, 0);
                        case TimeUnit.Months:
                            return new TimeSpan((int)(ResetTime * (yearValue / 12)), 0, 0, 0);
                        case TimeUnit.Years:
                            return new TimeSpan((int)(ResetTime * yearValue), 0, 0, 0);
                        default:
                            throw new ArgumentOutOfRangeException();
                    }
                }
            }

But I don't like it and it feels very double. Could anyone review this and refactor it, since I'm not able to see it.

private const double yearMultiplier = 365.2425;

private Dictionary> timespanConverters = new Dictionary>
{
    { TimeUnit.Seconds, TimeSpan.FromSeconds },
    { TimeUnit.Minutes, TimeSpan.FromMinutes },
    { TimeUnit.Hours,   TimeSpan.FromHours },
    { TimeUnit.Days,    TimeSpan.FromDays },
    { TimeUnit.Months, t => TimeSpan.FromDays((int)t * (yearMultiplier / 12))) },
    { TimeUnit.Years,  t => TimeSpan.FromDays((int)t * yearMultiplier)) }
}

// ....

public TimeSpan ResetTimeSpan
{
    get
    {
        return timespanConverters[ResetTimeUnitEnumValue](ResetTime);
    }
}

Bit of a shame that System.TimeSpan doesn't have FromMonths or FromYears methods otherwise this would look really neat :)

StackExchange Code Review Q#27552, answer score: 7