Volodymyr Bychkoviak wrote:
User has an input (javaScript calendar) on page where he can choose
some date to include in search. Search resolution is day resolution.
If user will enter same date in different time of date he will get
different results (because calendar will also set current hour and
minute in the date). But this is not right behavior.
I propose not to use GMT when rounding time to selected resolution.
This will prevent us from situation described above.
This can be done by replacing two lines "Calendar cal =
Calendar.getInstance(GMT);" with "Calendar cal = Calendar.getInstance();"
I don't think you're improving matters there: you might be
cancelling-out the effects of timezone adjustment when everyone is in
the same timezone, but if you have users on a browser in one timezone
and the server is in a different timezone then you're in for
interestingly broken results.
There's also the interesting decision about when a day starts. You're
using "Etc/GMT-2" instead of (for example) "Europe/Moscow" -- do you
have daylight savings time? What happens on the day the clocks
change? Is the answer different for spring and summer? If a document
is dated, let's say, 00:30 (half an hour after midnight) is its day
number dependent on the time zone? What's half an hour after midnight
when the clocks change?
You say you're using javascript to get a date in a browser -- would it
not be better to remove the time of day there and just leave you with
the date? And have the date as a string so you're not dealing with
boundary conditions?
When I was struggling with this for mail messages I eventually decided
that it really only makes sense to deal with GMT. If some client wants
messages delivered on, let say, 14-Jul-2006 then the client has to
produce the range of times that make most sense for it to be
14-Jul-2006. Here in the UK that's 13-Jul-2006 23:00:00 UTC to
14-Jul-2006 22:59:59. In San Francisco it would be 5pm to 5pm UTC, in
Moscow, well, you work it out. Of course, users in San Francisco,
Wokingham (where I am) and Moscow wouldn't see the same set of documents
dated 14-Jul-2006, but they'd none of them would see documents dated the
day before or the day after in their local timezone. If you want
everyone to see the same set of documents for Bastille Day then use UTC
throughout.
I'm not sure what you're doing in javascript, but it may be enough to
pass along the timezone correction along with the time and use that to
get the search that you want.
jch
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