Hour 24 to_s issue

[glindstr]

Not sure which module is responsible but there appears to be a bug when using Time with tzinfo and setting hour to 24.

# Time without tzinfo

puts Time.new(2022, 11, 6, 24, 0, 0)
# => 2022-11-07 00:00:00 -0600
puts Time.new(2022, 11, 6, 24, 0, 0).strftime("%Y-%m-%d %H:%M:%S %z")
# => 2022-11-07 00:00:00 -0600

# Time with tzinfo
tz = TZInfo::Timezone.get("America/Chicago")

puts Time.new(2022, 11, 6, 24, 0, 0, tzinfo=tz)
# => 2022-11-06 23:00:00 -0600      <== bug, off by one hour

puts Time.new(2022, 11, 6, 24, 0, 0, tzinfo=tz).strftime("%Y-%m-%d %H:%M:%S %z")
# => 2022-11-07 00:00:00 -0600

All the string outputs above should match (first two depends on your system timezone). The inconsistent issue appears to happen when using Time with hour = 24 and with tzinfo set.

ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x64-mingw-ucrt]
tzinfo (2.0.5, 2.0.4)
tzinfo-data (1.2022.1)

[philr]

I think the issue lies with Ruby's Time class.

Time.new(2022, 11, 6, 24, 0, 0, tzinfo=tz) calls tz.local_to_utc(t), where t is a Time-like instance representing 2022-11-07 00:00:00 UTC (UTC is expected - the offset of this instance is ignored by TZInfo). For America/Chicago, local_to_utc returns a Time instance representing 2022-11-07 06:00:00 UTC. That's the correct result (Chicago is 6 hours behind UTC at that time).

I'm not too familiar with the internals of the Time class. Perhaps significantly, Time#to_s produces a result without any further calls to tz. Time#strftime calls tz.utc_to_local(t) where t is a Time-like instance representing 2022-11-07 06:00:00 UTC. For America/Chicago, utc_to_local returns a TZInfo::TimeWithOffset (a subclass of Time) instance representing 2022-11-07 00:00:00 -0600.

I've noticed that there's also a difference in whether Time.new increments the day and resets the hour:

t1 = Time.new(2022, 11, 6, 24, 0, 0)
[t1.year, t1.month, t1.day, t1.hour]
# => [2022, 11, 7, 0]  <== converted to hour 0 on the next day

tz = TZInfo::Timezone.get("America/Chicago")
t2 = Time.new(2022, 11, 6, 24, 0, 0, tzinfo=tz)
[t2.year, t2.month, t2.day, t2.hour]
# => [2022, 11, 6, 24]  <== values left as supplied

It's probably best to raise this on the Ruby Issue Tracking System.

[glindstr]

Thank you for looking into this. I've added an issue #19106 to the ruby issue tracking system. I'll ask to reopen should it get kicked back this way.