template dur(string units)
@safe pure nothrow @nogc 
Duration
dur
 if (
units == "weeks" || 
units == "days"
 || 
units == "hours"
 || 
units == "minutes"
 || 
units == "seconds"
 || 
units == "msecs"
 || 
units == "usecs"
 || 
units == "hnsecs"
 || 
units == "nsecs"
)