How to Handle Daylight Savings Time in MySQL Datetime Fields?

Handling Daylight Savings Time in MySQL Datetime Fields

When using datetime fields in MySQL, specifying the time zone offset can pose a challenge, especially when dealing with daylight savings time (DST).

MySQL's datetime fields store timestamps directly, without applying timezone conversions. This means that timestamps may be ambiguous when stored in a timezone that observes DST. For instance, "2009-11-01 01:30:00" could refer to either 01:30:00 before or after the autumn "fall back."

To accurately store and retrieve time data amidst DST transitions, the following steps are recommended:

1. Use DATETIME Fields:

   • TIMESTAMP fields automatically convert timestamps to UTC and back, which can cause lossy roundtrips when using timezones with DST.
   • DATETIME fields, on the other hand, store timestamps as-is.

2. Convert Timezones Before Saving:

   • To ensure accurate storage, convert timestamps from the system timezone to a non-DST timezone (e.g., UTC) before saving to the database.

3. Convert Timezones Before Retrieving:

   • To accurately interpret retrieved timestamps, convert them from the UTC timezone back to the local system timezone using external functions outside MySQL (e.g., PHP's strtotime() or DateTime class).

4. Avoid MySQL Date/Time Math Functions:

   • MySQL's date/time math functions can malfunction around DST boundaries when dealing with timestamps stored in DST timezones.

By following these steps, you can reliably store and retrieve time data in MySQL, even when dealing with DST transitions, ensuring that timestamps are accurately recorded and represented.

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