如何初始化这个字典

我想初始化一个string,datetime字典中，我想要每个字符串的“实时”时间值。稍后我想将字符串作为键插入下拉列表中，将日期时间作为值插入。

1 hour (string)- datetime(1 hour value)  
5 hour (string)- datetime(5 hour value)  
2 days (string)- datetime(2 days value)  
3 weeks (string)-datetime(3 weeks value) 

怎样制作这样的词典呢？

public Dictionary<string,DateTime> TimeStep()
    {
        Dictionary<string,DateTime> timestep = 
        { "1  Hour", "2  Hours", "5  Hours", "10 Hours", "15 Hours", "24 Hours", "Two Days", "Five Days", "Ten Days", "Two Weeks", "Month" };
        return timestep ;        
    }

var dic = new Dictionary<string, TimeSpan>()
          {
                {"1  Hour", TimeSpan.FromHours(1)},
                {"Two days", TimeSpan.FromDays(2)}
          };