Time (and Date) doesn't always have equivalents of DateTime methods

Encountered a few issues trying to fix the style for spy. Those seem relatively minor but each change needs a lot more reflexion than I expected.

Time.parse doesn't end up with the same time zone

The 00:00 timezone information is not parsed the same way. Time seems to ignore the time zone information from the argument in this case (local time zone is currently UTC-4):

[2] pry(main)> DateTime.parse('2017-08-08T15:00:00 00:00').utc.iso8601
=> "2017-08-08T15:00:00+00:00"
[3] pry(main)> Time.parse('2017-08-08T15:00:00 00:00').utc.iso8601
=> "2017-08-08T19:00:00Z"

In this case Time.zone.parse is a more suitable replacement for DateTime.rfc3339.

Time.iso8601 prints UTC time zone differently

[1] pry(main)> DateTime.parse('2017-08-08T15:00:00Z').iso8601
=> "2017-08-08T15:00:00+00:00"
[2] pry(main)> Time.parse('2017-08-08T15:00:00Z').iso8601
=> "2017-08-08T15:00:00Z"

This is mostly harmless, but sometimes makes tests fail.

Date.rfc3339 timezone information is lost

[4] pry(main)> DateTime.rfc3339('2002-10-02T10:00:00-05:00').to_time.utc
=> 2002-10-02 15:00:00 UTC
[5] pry(main)> Date.rfc3339('2002-10-02T10:00:00-05:00').to_time.utc
=> 2002-10-02 04:00:00 UTC

Again, Time.zone.parse is a more suitable replacement for DateTime.rfc3339.

[bdewater]

Thanks for writing this up. IMO these issues highlight why adding the rule to our style guide was needed.

Time.parse doesn't end up with the same time zone

In this case you're trying to parse an almost ISO8601-like string (it's missing the +) and the parsing semantics are different: making the mixed use of Time and DateTime especially dangerous.

Here the second recommendation from #89 makes sense:

[9] pry(main)> Time.iso8601('2017-08-08T15:00:00 00:00')
ArgumentError: invalid date: "2017-08-08T15:00:00 00:00"
from /opt/rubies/2.3.1/lib/ruby/2.3.0/time.rb:598:in `xmlschema'
[10] pry(main)> a = Time.iso8601('2017-08-08T15:00:00+00:00')
=> 2017-08-08 15:00:00 +0000
[11] pry(main)> b = Time.iso8601('2017-08-08T15:00:00Z')
=> 2017-08-08 15:00:00 UTC
[12] pry(main)> a == b
=> true

Time.iso8601 prints UTC time zone differently

Yep, Z is military time zone 'Zulu'.

Date.rfc3339 timezone information is lost

Agree this can be a little confusing, but dates don't have time or time zones in Ruby. Again I'd push for using ISO8601 instead of parsing for strictness, but there's a nice speed gain as well: fastruby/fast-ruby#149