On Sun, Oct 21, 2012 at 7:30 AM, Matijn Woudt <tijn...@gmail.com> wrote:
> On Sun, Oct 21, 2012 at 12:01 PM, Maciek Sokolewicz
> <maciek.sokolew...@gmail.com> wrote:
>> On 21-10-2012 01:11, Karl DeSaulniers wrote:
>>>>> Thanks for the response. Yes, for the US I plan on calculating by
>>>>> state, but
>>>>> this website is not geared to just the US.
>>>>> So I am looking for a solution that lets me also calculate by
>>>>> country/region.
>>>>> Was looking on google and found geoip, but not sure if this will do
>>>>> the job
>>>>> I am looking for.
>>>>> Anyone with experience on geoip that can send pointers?
>>>>> Thanks,
>>>>> Best,
>>>>> Karl DeSaulniers
>>>>> Design Drumm
>>>>> http://designdrumm.com
>>>> Geo IP is based on IP, and I must warn you that IP data is not always
>>>> accurate. Especially here in Europe, companies that are based in
>>>> multiple countries sometimes only register their IPs in a single
>>>> country, and share them between all the countries they are active in.
>>>> This will give you wrong data from GeoIP. The time difference will
>>>> only be 1 hour at max, but still.
>>> That was what my own suspicions were leading to.
>>> I am familiar with the fact that ips can be spoofed.
>>> Thanks for the corroboration.
>>> Best,
>>> Karl DeSaulniers
>>> Design Drumm
>>> http://designdrumm.com
>> As Bart said, IP is not ideal for this situation.
>> Since you do have information about the location of that person (as in
>> country and possible state), you can find out the timezone via a static
>> database.
>> The HTML5 geolocation tool is nice, and would certainly help a lot! However,
>> be aware of the fact that it only works if there is the device on which the
>> browser runs actually has the ability to find out its location. Many
>> smartphones have GPS chips, but most PCs don't. Asking a PC "where are you
>> located?" the PC will answer "How should I know?".
>> Luckily for you, the way of country and state is pretty easy. I've handed
>> you a list to find it in the USA. For most countries in the world, there's a
>> simple 1:1 mapping of timezone and country
>> (http://en.wikipedia.org/wiki/List_of_time_zones_by_country), there are
>> however 21 countries which have multiple timezones. In these cases, you'll
>> need extra information to be able to distinguish between them.
>> For the USA, you already have a way.
>> For (ex-)colonical islands and such (such as for France), you could always
>> add them to the country list:
>> - France
>> - France (Marquesas Islands)
>> - France (Gambier)
>> etc.
>> Thus treating them as separate countries for your timezone db.
>> In Russia, Canada, Australia, New Zealand, Brasil, Indonesia, Kiribati,
>> Mexico,Congo, Ecuador, Micronesia, Kazakhstan and Mongolia you'll need to
>> know their province / state to more accurately assess the ideal timezone.
>> So for most countries, it's a simple 1:1 translation. For the above
>> countries, you'll need some extra info, and translate further based on that.
>> You should be able to find the info required yourself, it just takes a while
>> to collect it.
>> Alternatively, and this is the most simple way; since you're asking people
>> for their country and such, simply also ask them about their timezone. Don't
>> bother automating and putting a heck of a lot of time into hard to realize
>> solutions, when you can ask a very simple and easy-to-answer question to the
>> browser instead. :)
>> - Tul
> Don't forget that some countries have DST, and some don't. And those
> that have DST, all use different dates.. So in to keep a static
> database you would also need to have DST info from all countries.
> - Matijn

Using the standard labels in /usr/share/zoneinfo should be able to
avoid having to keep track of who is and isn't in DST, *provided* you
find a way to map the user's address to one of those files.

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