try/catch idiom in std.datetime

[Walter Bright]

On 11/17/2013 10:32 PM, Andrei Alexandrescu wrote:
> 4. ...?

Revisit why removeUnitsFromHNSecs, etc., are throwing. Since the caller is 
guaranteeing they don't throw, I suspect the runtime data validation is itself 
invalid and the throws should be replaced with asserts.