[tz] please do not enforce limits in code for time zones

[Paul.Koning at dell.com]

> On Jan 22, 2018, at 2:42 PM, Random832 <random832 at fastmail.com> wrote:
> 
> On Mon, Jan 22, 2018, at 13:55, Steve Allen wrote:
>> The traditional calendar for observing at Lick Observatory has always
>> had days begin at local noon.  This means that the time zone for the
>> Lick calendar is 20 hours behind Greenwich. 
> 
> Wouldn't that make local noon midnight? 

Yes, that's the whole point.  Astronomers (the non-solar kind) like it when the date doesn't change in the middle of their work day.  

If you use am/pm style timestamps, it gets somewhat confusing (unless you read "m" as "media nocte" rather than "meridiem" :-) ) but with 24 hour timestamps it's pretty reasonable.

	paul