Hello tzdata maintainers,
 

 
I would like to propose a feature enhancement for the zic compiler.
 


 
Currently, the NOS time zone rules are defined as:
 


 
Rule NOS 1970 2037 - Jan 27 23:43:01 2:0 SDST
 
Rule NOS 1970 2037 - Jan 28 0:51:01 0 S
 
Zone OS/NOS +7:0:0 NOS NO%s
 


 
Issue:
 
- The first rule enters DST at 23:43:01 with a +2 hour offset, moving local 
time to 01:43:01.
 
- The second rule is intended to revert to standard time at 00:51:01.
 
- Due to the offset, 00:51:01 local time never occurs, so the second rule will 
never trigger.
 
- This creates unreachable local times and may cause incorrect results in time 
calculations.
 


 
Proposal:
 
- Add validation in the zic command to detect DST rules where the offset causes 
the subsequent rule's local time to be unreachable.
 
- The validation could issue a warning or error to alert the author of 
potentially invalid rules.
 
- This would improve the robustness of time zone definitions and prevent subtle 
bugs in downstream applications.
 


 
Thank you for your consideration.
 


 
Best regards

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