Fix to_datetime() for datetimes before the epoch

[aferreira]

I found the issue when representing birth dates with Mango::Time objects - calling to_datetime on a date before the epoch like 1965-12-21 would emit uninit warnings and end up with Jan 1, 1970 as output.

The bug comes from

https://github.com/oliwer/mango/blob/master/lib/Mango/BSON/Time.pm#L12 which in turn points

to Mojo::Date code

https://github.com/kraih/mojo/blob/master/lib/Mojo/Date.pm#L25

I tried to fix the issue downstream in Mojo::Date

• Mojo::Date: epoch can be a negative number mojolicious/mojo#1079

• Mojo::Date: negative & fractional epoch mojolicious/mojo#1080

but those patches have been rejected: the first due to failing extra tests added for negative fractional epoch, and the second because it was not elegant enough.

This time, this patch is meant to make Mango::BSON::Time to replace Mojo::Date->new($epoch) (which does not work for dates before Jan 1, 1970) with Mojo::Date->new->epoch($epoch).

[aferreira]

This is the output of t/bson.t with the extra tests on 5dd139e and before the fix on dee3371:

$ prove --blib t/bson.t
t/bson.t .. 1/? Use of uninitialized value $epoch in gmtime at /Users/ferreira/.perlbrew/libs/perl-5.22.2@tmp3/lib/perl5/Mojo/Date.pm line 57.
Use of uninitialized value $epoch in pattern match (m//) at /Users/ferreira/.perlbrew/libs/perl-5.22.2@tmp3/lib/perl5/Mojo/Date.pm line 60.

#   Failed test 'Before epoch: Boris Karloff death'
#   at t/bson.t line 61.
#          got: '1970-01-01T00:00:00Z'
#     expected: '1969-02-02T11:00:00Z'
Use of uninitialized value $epoch in gmtime at /Users/ferreira/.perlbrew/libs/perl-5.22.2@tmp3/lib/perl5/Mojo/Date.pm line 57.
Use of uninitialized value $epoch in pattern match (m//) at /Users/ferreira/.perlbrew/libs/perl-5.22.2@tmp3/lib/perl5/Mojo/Date.pm line 60.

#   Failed test 'Well before epoch: Battle of New Orleans'
#   at t/bson.t line 63.
#          got: '1970-01-01T00:00:00Z'
#     expected: '1815-01-08T17:44:38Z'
# Looks like you failed 2 tests of 182.
t/bson.t .. Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/182 subtests 

Test Summary Report
-------------------
t/bson.t (Wstat: 512 Tests: 182 Failed: 2)
  Failed tests:  25-26
  Non-zero exit status: 2
Files=1, Tests=182,  0 wallclock secs ( 0.02 usr  0.00 sys +  0.11 cusr  0.01 csys =  0.14 CPU)
Result: FAIL

[aferreira]

Side note about dates used for the tests (not important for the test itself):

Where these dates came from?

I used the epoch computed with DateTime 1.43 and DateTime::Format::Strptime 1.73

1. Boris Karloff death

   DateTime::Format::Strptime->new(pattern => '%Y-%m-%d %H:%M', time_zone => 'Europe/London')
   ->parse_datetime('1969-02-02 12:00')
   ->epoch

   -28731600
   1969-02-02T11:00:00Z

2. Battle of New Orleans

   DateTime::Format::Strptime->new(pattern => '%Y-%m-%d %H:%M', time_zone => 'America/Indianapolis')
   ->parse_datetime('1815-01-08 12:00')
   ->epoch

   -4890694522
   1815-01-08T17:44:38Z

[aferreira]

@oliwer Let me know what you think about this patch.

[oliwer]

Thanks @aferreira. This looks good to me. And it's nice to add some cultural references. I'll try to make a release this weekend.