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Editorial Team
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Asked: 2026-05-27T20:17:57+00:00

I store a date/time in my database that is UTC. I’m working to add

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I store a date/time in my database that is UTC. I’m working to add conversion of this once a user selects a timezone so it shows local time for them. Basically the user selects from a form:

<select name="DropDownTimezone" id="DropDownTimezone">
   <option value="-12.0">(GMT -12:00) Eniwetok, Kwajalein</option>
   <option value="-11.0">(GMT -11:00) Midway Island, Samoa</option>
   <option value="-10.0">(GMT -10:00) Hawaii</option>
   ...

I can make the option value anything I want but an easy to remember one is as above. What data type would I use for mysql? Does it really matter in this case? Would TINYINT do? Maybe using an ENUM would be a good idea?

Any suggestions would be appreciated.

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1 Answer

  1. Editorial Team

    The scheme you’re proposing (storing time zones as an integer offset from GMT) may fail for the following cases:

    • India, which is on UTC + 05:30 (not an integer number of hours).
    • Kiribati, which is on UTC + 14:00 (over 12 hours).
    • Distinguishing British Time and GMT. (The former uses Daylight Saving Time; the latter is not.)
    • Distinguishing between some pairs of countries which use the same GMT offset, but which switch at different times of the year.

    For full time zone support, I’d recommend using the zoneinfo database and storing time zones as strings (e.g, “America/New_York”).

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