[PHP] Dates and different time zones
Hello, I am creating an international site that is going to get used in both American and Europe. And I wonder how to handle the different time zones, because I want the date and time to be correct after the place your using the application. I now have the date_default_timezone_set() to Europe/Stockholm, and all dates that is saved into the database is timestamp with time zone (using PostgreSQL). So a wonder who to handle different time zones? Have any of your experience of this? Cheers Niklas Karlsson
RE: [PHP] Dates and different time zones
[snip] So a wonder who to handle different time zones? Have any of your experience of this? [/snip] The server lives in one time zone and therefore cannot handle multiples unless there is some new widget available for this. There are a couple of methods available; 1. Use JavaScript to capture 'local' (client-side) time to a PHP variable. 2. Use time zone offsets for ranges of IP addresses known to be in each time zone. -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
Niklas Karlsson wrote: I am creating an international site that is going to get used in both American and Europe. And I wonder how to handle the different time zones, because I want the date and time to be correct after the place your using the application. I now have the date_default_timezone_set() to Europe/Stockholm, and all dates that is saved into the database is timestamp with time zone (using PostgreSQL). So a wonder who to handle different time zones? Have any of your experience of this? Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Cheers, Rich -- Zend Certified Engineer http://www.corephp.co.uk Never trust a computer you can't throw out of a window -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
- Original Message - From: Richard Davey [EMAIL PROTECTED] To: php-general@lists.php.net Sent: Tuesday, April 10, 2007 3:43 PM Subject: Re: [PHP] Dates and different time zones Niklas Karlsson wrote: I am creating an international site that is going to get used in both American and Europe. And I wonder how to handle the different time zones, because I want the date and time to be correct after the place your using the application. I now have the date_default_timezone_set() to Europe/Stockholm, and all dates that is saved into the database is timestamp with time zone (using PostgreSQL). So a wonder who to handle different time zones? Have any of your experience of this? Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Actually, I find that it is better not to bother storing anything for the user at all. At the first chance, get some JavaScript to read the local time of the client machine and send it back to the server, either with the login data, using some AJAX or along with any link the user might click on the welcome screen, for example, the language choice. Then use the offset from his local time to the server time for every time information, substract it from any time information you read from them, add it to anything you send them. This works whether the user is registered or not, whether he/she travels or remains in the same time zone and spares you the trouble of keeping your IP to country to timezone table updated. It assumes that the user updates the time zone on his/her machine and if he doesn't it means she doesn't care, so why should you. (some travellers prefer to keep their portable machines set to their home-base time zone) Satyam Cheers, Rich -- Zend Certified Engineer http://www.corephp.co.uk Never trust a computer you can't throw out of a window -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.0.0/754 - Release Date: 09/04/2007 22:59 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
Satyam wrote: Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Actually, I find that it is better not to bother storing anything for the user at all. At the first chance, get some JavaScript to read the local time of the client machine and send it back to the server, either with the login data, using some AJAX or along with any link the user might click on the welcome screen, for example, the language choice. Then use the offset from his local time to the server time for every time information, substract it from any time information you read from them, add it to anything you send them. This works whether the user is registered or not, whether he/she travels or remains in the same time zone and spares you the trouble of keeping your IP to country to timezone table updated. It assumes that the user updates the time zone on his/her machine and if he doesn't it means she doesn't care, so why should you. (some travellers prefer to keep their portable machines set to their home-base time zone) Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The only way to get this working properly at present is to get the user to set their time/daylight settings in their profile, and then you can provide the correct offset for all days on a calendar. Remember that for users WITH a daylight saving offset, one day each year has 23 hours and one 25 hours ;) -- Lester Caine - G8HFL - Contact - http://home.lsces.co.uk/lsces/wiki/?page=contact L.S.Caine Electronic Services - http://home.lsces.co.uk MEDW - http://home.lsces.co.uk/ModelEngineersDigitalWorkshop/ Treasurer - Firebird Foundation Inc. - http://www.firebirdsql.org/index.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
- Original Message - From: Lester Caine [EMAIL PROTECTED] To: php-general@lists.php.net Sent: Tuesday, April 10, 2007 4:37 PM Subject: Re: [PHP] Dates and different time zones Satyam wrote: Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Actually, I find that it is better not to bother storing anything for the user at all. At the first chance, get some JavaScript to read the local time of the client machine and send it back to the server, either with the login data, using some AJAX or along with any link the user might click on the welcome screen, for example, the language choice. Then use the offset from his local time to the server time for every time information, substract it from any time information you read from them, add it to anything you send them. This works whether the user is registered or not, whether he/she travels or remains in the same time zone and spares you the trouble of keeping your IP to country to timezone table updated. It assumes that the user updates the time zone on his/her machine and if he doesn't it means she doesn't care, so why should you. (some travellers prefer to keep their portable machines set to their home-base time zone) Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The point is that you don't store the time offset in any user profile or anywhere but a session variable, which you keep for the duration of the session so it lasts only while the user is connected, whether logged in or not, profile or not. Next time he/she connects you get the new offset. If the time has changed due to daylight savings or the user travelling elsewhere, you'll get a new offset. The only time it fails is if the user is connected while the time switch is happening, but so will most of the clocks, watches and whatever is on at the time. Satyam The only way to get this working properly at present is to get the user to set their time/daylight settings in their profile, and then you can provide the correct offset for all days on a calendar. Remember that for users WITH a daylight saving offset, one day each year has 23 hours and one 25 hours ;) -- Lester Caine - G8HFL - Contact - http://home.lsces.co.uk/lsces/wiki/?page=contact L.S.Caine Electronic Services - http://home.lsces.co.uk MEDW - http://home.lsces.co.uk/ModelEngineersDigitalWorkshop/ Treasurer - Firebird Foundation Inc. - http://www.firebirdsql.org/index.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.0.0/754 - Release Date: 09/04/2007 22:59 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP] Dates and different time zones
Thanks for good answers. Okay, so I should set the default time zone to central GMT time, and then save GMT offset for every user. This sounds realistic, because I don't think that I need to correct the time for users that doesn't login. So, if I now have the GMT offset for every user, how do I display the right date? Can someone please show some phpcode? I would be very grateful if someone could do that. Satyam wrote: Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Actually, I find that it is better not to bother storing anything for the user at all. At the first chance, get some JavaScript to read the local time of the client machine and send it back to the server, either with the login data, using some AJAX or along with any link the user might click on the welcome screen, for example, the language choice. Then use the offset from his local time to the server time for every time information, substract it from any time information you read from them, add it to anything you send them. This works whether the user is registered or not, whether he/she travels or remains in the same time zone and spares you the trouble of keeping your IP to country to timezone table updated. It assumes that the user updates the time zone on his/her machine and if he doesn't it means she doesn't care, so why should you. (some travellers prefer to keep their portable machines set to their home-base time zone) Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The only way to get this working properly at present is to get the user to set their time/daylight settings in their profile, and then you can provide the correct offset for all days on a calendar. Remember that for users WITH a daylight saving offset, one day each year has 23 hours and one 25 hours ;) -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
Niklas Karlsson wrote: Okay, so I should set the default time zone to central GMT time, and then save GMT offset for every user. This sounds realistic, because I don't think that I need to correct the time for users that doesn't login. So, if I now have the GMT offset for every user, how do I display the right date? Can someone please show some phpcode? I would be very grateful if someone could do that. It depends where the dates are coming from. My guess would be a database, and if so why not let MySQL do the work for you? SELECT date_created, DATE_SUB(date_created, INTERVAL 8 HOUR) AS offset_date from your_table The above assumes the users offset is -8 hours. Use DATE_ADD for GMT + values. Then you'll have both values in PHP - the actual original GMT date the date was created, and an offset date you can use for display. Or of course you can pluck just the GMT date out and start using PHP functions to convert to local timezones, etc. But if the shoe fits ... Cheers, Rich -- Zend Certified Engineer http://www.corephp.co.uk Never trust a computer you can't throw out of a window -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
Satyam wrote: Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The point is that you don't store the time offset in any user profile or anywhere but a session variable, which you keep for the duration of the session so it lasts only while the user is connected, whether logged in or not, profile or not. Next time he/she connects you get the new offset. If the time has changed due to daylight savings or the user travelling elsewhere, you'll get a new offset. The only time it fails is if the user is connected while the time switch is happening, but so will most of the clocks, watches and whatever is on at the time. Please read what I wrote. The time offset from the browser is only of use to map CURRENT time. It is no use to display dates and times stored in the database that are reliant on the daylight saving offset. If TOMORROW is after the change in daylight saving, then the browser offset will not give you the right offset for tomorrows. The problem is convincing people that there *IS* a real problem, and trying to display the correct times JUST from a timezone offset is wrong for at least half of the year! You need to know that the time is changing tonight so that you can display tomorrows calendar correctly? -- Lester Caine - G8HFL - Contact - http://home.lsces.co.uk/lsces/wiki/?page=contact L.S.Caine Electronic Services - http://home.lsces.co.uk MEDW - http://home.lsces.co.uk/ModelEngineersDigitalWorkshop/ Treasurer - Firebird Foundation Inc. - http://www.firebirdsql.org/index.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
- Original Message - From: Niklas Karlsson [EMAIL PROTECTED] To: php-general@lists.php.net Sent: Tuesday, April 10, 2007 5:32 PM Subject: RE: [PHP] Dates and different time zones Thanks for good answers. Okay, so I should set the default time zone to central GMT time, and then save GMT offset for every user. This sounds realistic, because I don't think that I need to correct the time for users that doesn't login. Well, that was my whole point. If you store the GMT offsets for each user at a certain time in the year, they will turn invalid when they switch from daylight savings to no savings. Not all countries use daylight savings and even those that do don't switch at the same time. Furthermore, northern and southern hemispheres switch in opposite directions, if and when they do. If your users have to log in, that is the perfect time to read their current local time from the browser and keep it just for the session. Don't store it permanently. In PHP dates are stored as seconds from an arbitrary zero set at Jan 1st, 1970, so does MySql with date/time values though it shows them formatted but you can use the UNIX_TIMESTAMP function to get the actual timestamp. JavaScript uses milliseconds from the same base date. The rest is plain arithmetic. Satyam So, if I now have the GMT offset for every user, how do I display the right date? Can someone please show some phpcode? I would be very grateful if someone could do that. Satyam wrote: Store all of your dates as GMT. Perform all date based calculations around GMT also, and then offset the values for localised display only. This way you only need to store the GMT offsets for each user, i.e. GMT+1 or GMT-8 when it comes to displaying the dates to them. The trick is to use a constant base date for all data, and only being the user timezones into play when needed. Actually, I find that it is better not to bother storing anything for the user at all. At the first chance, get some JavaScript to read the local time of the client machine and send it back to the server, either with the login data, using some AJAX or along with any link the user might click on the welcome screen, for example, the language choice. Then use the offset from his local time to the server time for every time information, substract it from any time information you read from them, add it to anything you send them. This works whether the user is registered or not, whether he/she travels or remains in the same time zone and spares you the trouble of keeping your IP to country to timezone table updated. It assumes that the user updates the time zone on his/her machine and if he doesn't it means she doesn't care, so why should you. (some travellers prefer to keep their portable machines set to their home-base time zone) Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The only way to get this working properly at present is to get the user to set their time/daylight settings in their profile, and then you can provide the correct offset for all days on a calendar. Remember that for users WITH a daylight saving offset, one day each year has 23 hours and one 25 hours ;) -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.0.0/754 - Release Date: 09/04/2007 22:59 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
You are totally right, I am sorry. I would hate to miss my plane or train due to such mistake. Satyam - Original Message - From: Lester Caine [EMAIL PROTECTED] To: php-general@lists.php.net Sent: Tuesday, April 10, 2007 6:29 PM Subject: Re: [PHP] Dates and different time zones Satyam wrote: Of cause the major fault with this is that it can only display the CURRENT time offset. You *ALSO* need the users Daylight Saving Zone as well. This has been giving us great fun since the winter dates and times need a different offset to the summer ones. Something that simplistic browser time offset does not supply. :( The point is that you don't store the time offset in any user profile or anywhere but a session variable, which you keep for the duration of the session so it lasts only while the user is connected, whether logged in or not, profile or not. Next time he/she connects you get the new offset. If the time has changed due to daylight savings or the user travelling elsewhere, you'll get a new offset. The only time it fails is if the user is connected while the time switch is happening, but so will most of the clocks, watches and whatever is on at the time. Please read what I wrote. The time offset from the browser is only of use to map CURRENT time. It is no use to display dates and times stored in the database that are reliant on the daylight saving offset. If TOMORROW is after the change in daylight saving, then the browser offset will not give you the right offset for tomorrows. The problem is convincing people that there *IS* a real problem, and trying to display the correct times JUST from a timezone offset is wrong for at least half of the year! You need to know that the time is changing tonight so that you can display tomorrows calendar correctly? -- Lester Caine - G8HFL - Contact - http://home.lsces.co.uk/lsces/wiki/?page=contact L.S.Caine Electronic Services - http://home.lsces.co.uk MEDW - http://home.lsces.co.uk/ModelEngineersDigitalWorkshop/ Treasurer - Firebird Foundation Inc. - http://www.firebirdsql.org/index.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 269.0.0/754 - Release Date: 09/04/2007 22:59 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
On Tue, April 10, 2007 11:49 am, Satyam wrote: You are totally right, I am sorry. I would hate to miss my plane or train due to such mistake. Can somebody with way more karma than me put in an RFC to just NUKE daylight savings? Pretty please? Thanks! Whatever alleged benefits there are, they cannot possibly outweigh the drawbacks. Time zones at :15 intervals are bad enough! -- Some people have a gift link here. Know what I want? I want you to buy a CD from some indie artist. http://cdbaby.com/browse/from/lynch Yeah, I get a buck. So? -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Dates and different time zones
On Tue, April 10, 2007 11:38 am, Satyam wrote: In PHP dates are stored as seconds from an arbitrary zero set at Jan 1st, 1970, so does MySql with date/time values though it shows them formatted but nitpick: I don't think MySQL uses Unix timestamp internally, as it's quite capable of storing a wider range than Unix timestamp. I could be wrong, of course, depending on what data type you were thinking of, and what version of MySQL, and what server settings are in effect... Databases have a bewildering plethora of date/time storage options. :-) -- Some people have a gift link here. Know what I want? I want you to buy a CD from some indie artist. http://cdbaby.com/browse/from/lynch Yeah, I get a buck. So? -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
