[tz] Epic fail for DST fallback in hospital health records

Lester Caine lester at lsces.co.uk
Thu Nov 8 08:44:22 UTC 2018

On 08/11/2018 08:26, Guy Harris wrote:
>> As ever it's not as simple as that. Much of this software comes from mainframe days when these problems were not so 'well known'.
> Daylight Savings Time was "well known" long before computers were used for hospital record keeping.

My own involvement with systems having problems with changes in time 
relates to railway systems 25+ years ago. At that time the UK trains did 
not run over night but it was coming in and we switched the underlying 
systems to UTC. As a side 'effect' it also solved problems with cross 
channel train movements since the Channel Tunnel had just opened!

>> I doubt there were any specifications and nobody thought about transferring patients across timezones.
> This isn't an issue of transferring patients across timezones.  It's an issue of "what happens when the clock gets turned back?"

THAT is exactly the sort of statement that causes problems with any 
developments. It's just like the ones about historic time rules not 
being important. If one DESIGNS systems these days to be able to handle 
common activity then the risk of unexpected problems is reduced? The 
hospital records problem is only partially fixed by bodging over the 
time change. Fixing the problem properly by adopting UTC for all record 
storage prevents patients perhaps getting medication too early because 
they have been transferred 'down the road' to a better equipped facility 
... in another time zone.

Lester Caine - G8HFL
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