129 tests failed. preparse_postformat:calendar day (223.5) ... and many others

[mattjohnsonpint]

Running on Windows 8, time zone set to almost any European zone (London, Paris, several others). All browsers (IE10, FF24, Chrome 30) are failing with multiple errors starting with:

preparse_postformat:calendar day (223.3)

Now plus 1 hour

// Expected Today at #:)) AM
// Actual   Today at @:)) AM
"Today at @:)) AM" == "Today at #:)) AM"

Then followed by these errors in every language. (showing the english ones):

lang:en:calendar day (622.3)

Now plus 1 hour

// Expected Today at 3:00 AM
// Actual   Today at 2:00 AM
"Today at 2:00 AM" == "Today at 3:00 AM"

lang:en:calendar next week (623.2)

Today + 2 days beginning of day

// Expected Tuesday at 12:00 AM
// Actual   Tomorrow at 12:00 AM
"Tomorrow at 12:00 AM" == "Tuesday at 12:00 AM"

[icambron]

Yikes!

[mattjohnsonpint]

Also note that today is October 27th 2013, which is the day that DST ends in Europe. I suspect we will encounter these problems in other time zones as well, such as November 3rd 2013 in the USA.

[icambron]

OK, if I get some time this evening, I'll take a crack at it and see if I can figure it out; I thought this stuff was robust across DSTs.

BTW, thanks for all this testing work!

[icambron]

The culprit appears to be #1019. The logic there (adjust for moments with offsets) conflicts with the cross-DST stuff in diff(), because it double-corrects. Removing either of the adjustments does the trick, but break other stuff. I probably need to work this through without trying to watch a baseball game at the same time.