(As long as the specific implementation returns base::Time() on failure the rest of the code will work as expected, but that isn't promised in the API. Won't know until testing the platform-specific implementations if it holds)

According to the Internet mktime allows some invalid times, at least - subtract 100 from month, for example, to get a time 100 months previous.  Seems like that adding 2 to a day, like Feb. 28, could do the same.

Maybe go from exploded to Time and then back, and compare the values?

That is true of mktime, but not generally true of base::Time::FromUTCExploded(). Since under the hood the Windows implementation accepts a very different set of values, and out of range days/months don't have that same semantic meaning.

This is a problem with our FromUTCExploded() API as described in the parent bug. It is unpredictable with how it will handle different values (what it considers failures), and is also inconsistent in how it reports "errors".

As a first approximation the various exploded checks here could be replaced by exploded.HasValidValues(). (1601 for instance is the Windows epoch in there, and 1970 is the minimum year the posix one supports.)

Round-tripping would be a good workaround as you mention.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3d0a1b68b407f0535052b62819f9e7bb68ee2a94

commit 3d0a1b68b407f0535052b62819f9e7bb68ee2a94
Author: maksim.sisov <maksim.sisov@intel.com>
Date: Thu Jun 30 09:59:36 2016

Make callers of FromUTC(Local)Exploded in third_party/ use new time API.

Use new time conversion API in accordance with
https://codereview.chromium.org/1988663002/

BUG= 601905 

Review-Url: https://codereview.chromium.org/2091673002
Cr-Commit-Position: refs/heads/master@{#403134}

[modify] https://crrev.com/3d0a1b68b407f0535052b62819f9e7bb68ee2a94/third_party/zlib/google/zip_reader.cc
[modify] https://crrev.com/3d0a1b68b407f0535052b62819f9e7bb68ee2a94/third_party/zlib/google/zip_unittest.cc

Comment 5 is wrong.

I used wrong bug number by accident. Comment 5 issue concerns https://bugs.chromium.org/p/chromium/issues/detail?id=601908

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c8c6cd130d570c7b269e6c10e6716631afd3a648

commit c8c6cd130d570c7b269e6c10e6716631afd3a648
Author: maksim.sisov <maksim.sisov@intel.com>
Date: Tue Dec 20 13:36:00 2016

Make callers of FromUTC(Local)Exploded in net/ use new time API.

Use new time conversion API in accordance with
https://codereview.chromium.org/1988663002/

BUG= 601905 , 601903 , 601900 

Review-Url: https://codereview.chromium.org/2090713003
Cr-Commit-Position: refs/heads/master@{#439789}

[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/cert/ct_policy_enforcer_unittest.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/cert/x509_cert_types.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/cert/x509_cert_types_unittest.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/disk_cache/blockfile/eviction.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/extras/sqlite/sqlite_channel_id_store_unittest.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/ftp/ftp_directory_listing_parser_ls.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/ftp/ftp_directory_listing_parser_unittest.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/ftp/ftp_directory_listing_parser_unittest.h
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/ftp/ftp_directory_listing_parser_vms.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/ftp/ftp_util.cc
[modify] https://crrev.com/c8c6cd130d570c7b269e6c10e6716631afd3a648/net/http/http_util_unittest.cc

I guess we can close it now.