Many applications solve this by asking users their timezone at the time of registration and display part is more or less solved in this way. Most of the time these applications ask about your country and figure out by themselves about the timezone but there are some countries which are having multiple timezones and in that case time zone offset is used in GMT+- hh:mm format.

Problem arises when you also need to support the day light saving time. And it becomes more important when you need to do more than just displaying few values to the user like contacting certain people of certain timezone in certain time range.

There are ways to do support all different timezones with day light saving time and actually supported in many languages/platforms like Java and .Net. This is implemented using Zone info Database or Olsen Database

Mysql also provides this functionality but not in very standard way and probably that is the reason for non-popularity of this function. Another reason is that it requires some extra arrangements to use this function i.e. populating some of the timezone tables in mysql schema.

Here is the usage of this function:

1. SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET');

2. SELECT CONVERT_TZ(UTC_TIMESTAMP(),'GMT','MST');

Before using this function, just make sure that you have populated some of the timezone tables in mysql schema.

a. time_zone
b. time_zone_leap_second
c. time_zone_name
d. time_zone_transition
e. time_zone_transition_type

You can get these tables at http://dev.mysql.com/downloads/timezones.html and see more information about MySql timezone support at http://dev.mysql.com/doc/refman/5.0/en/time-zone-support.html

Here is an example of this function with the use case, suppose you want to send an e-mail to the user of your application on his birthday and users belong to multiple timezones having day light saving time. If you have following information , you can actually greet your user for his birthday as soon as date changes to his B’Day.

You need to run a thread every 5 minutes to check if any of your users have birthday.

a. user’s timezone information
b. user’s birth date.

SELECT DATE(CONVERT_TZ(UTC_TIMESTAMP(),'GMT','users-time-zone'));

if result is equal to the user’s birth date, you can send him B’Day wishes.

Many times you take pictures or videos using your camera and want to use them on different device e.g. if I want to rip the DVD and watch movie on my cell phone, I need to convert the DVD media into some format which is supported by my mobile and conversion should also take care of rest of the parameters so that video can be seen on phone in best possible quality.

Use of phone increased a lot and that makes it more required to have some tool which can convert among different media file formats easily. I am sure there are many such software tool which does the required thing which i tried to describe above but here i have one solution which I use and also quite happy with it.

FormatFactory is the software which can solve all the requirements for converting media from one format and specifications to other format and specifications. You can download this from www.pcfreetime.com and also find more details about it.

Here is a glimpse of all the features:

1. support converting all popular video,audio,picture formats to others (All to MP4/3GP/MPG/AVI/WMV/FLV/SWF, All to MP3/WMA/AMR/OGG/AAC/WAV, All to JPG/BMP/PNG/TIF/ICO/GIF/TGA, Rip DVD to video file , Rip Music CD to audio file, MP4 files support iPod/iPhone/PSP/BlackBerry format,
Supports RMVB,Watermark, AV Mux)
2. Repair damaged video and audio file.
3. Reducing Multimedia file size.
4. Support iphone,ipod multimedia file formats
5. Picture converting supports Zoom,Rotate/Flip,tags.
6. DVD Ripper.
7. Supports 50 languages

You can go through the help section after installing the software, in case you find any difficulty in usage.

it has a separate option for converting media (audio/video) for mobile devices which contains wide range of brands and their devices (having predefined requirements of format and other specifications) which made the conversion really easy as you do not need to learn all about media format support of your device.

Go to options for changing different settings like the output folder of converted media, after conversion actions and more media format related options.

Note: You can also use format factory from command shell. How? Go through the help section from Help menu.