# DateDifference problem in v11

Bug introduced in v11, fixed in v11.1

I have recently upgraded to Mathematica 11. Here is a simplified version of code that worked in v10.2:

mn = DateObject[
DateValue[DateObject[], {"Year", "Month", "Day"}],
TimeZone -> LocalTimeZone[]];

DateDifference[mn, mn]


The results is an error with the message:

  DateDifference::date: Expression {Gregorian,Thu 15 Dec 2016EST} cannot
be interpreted as a date specification.


In v10.2, the computed and expected result is 0 days.

I could not find any documentation that mentions a relevant change in DateDifference in v11.

My question is: am I missing anything? If not, how should I go about reporting this issue?

• DateDifference[DateList@mn, DateList@mn]. But yeah, you shouldn't have to do that. – KAI Dec 15 '16 at 17:48
• Anyway, the problem is the LocalTimeZone[]. Note that if you change it to 0, the code works. – KAI Dec 15 '16 at 17:52
• Or use TimeZone -> \$TimeZone – Bob Hanlon Dec 23 '16 at 14:19