Issue #14879 has been updated by ioquatix (Samuel Williams).


I have added some specs for this behaviour here: https://github.com/ioquatix/time-zone/blob/cdde65cd8f29d6d9fc645e2182093a7146048b44/spec/time/zone_spec.rb#L91-L99

You can see test results here: https://travis-ci.org/ioquatix/time-zone

The work around for this bug was to convert whatever is the resulting time back into the correct timezone: https://github.com/ioquatix/time-zone/blob/cdde65cd8f29d6d9fc645e2182093a7146048b44/lib/time/zone/timestamp.rb#L79-L82

I'm open to suggestions for ways to improve this.

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Bug #14879: Adding/subtracting from time can change utc_offset unexpectedly.
https://bugs.ruby-lang.org/issues/14879#change-72699

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
I have been having some problems with `Time`. When I add or subtract seconds, sometimes the utc_offset is changed unexpectedly.

```
$ ruby -e 'require "time"; puts Time.parse("5pm NZT")'            
2018-06-29 17:00:00 +1200

$ ruby -e 'require "time"; puts Time.parse("5pm NZT") + 1'
2018-06-29 17:00:01 +1200

$ TZ=UTC ruby -e 'require "time"; puts Time.parse("5pm NZT") + 1'
2018-06-29 17:00:01 +0000
```

This seems like strange behaviour. The `utc_offset` shouldn't change IMHO.



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