Difference Between Two datetimes

[Roy Smith]

In article <hh9k6g$pkq$3 at news.eternal-september.org>,
 "W. eWatson" <wolftracks at invalid.com> wrote:

> BTW, all times are local to my city. Same time zone.

Yes, but how much time has elapsed between "2009/0/04 13:01:15" and 
"2009/06/04 13:01:15"?  Even if I tell you that both timestamps were done 
in the same city, you don't have enough information.

Hint #1: The answer in Sydney, Bangalore, and New York are all different.

Hint #2: Two of those cities are in temperate zones, and one is in the 
tropics.

Hint #3: If you don't pay attention to this, you will be bitten twice a 
year.