Showing posts with label Timezone. Show all posts
Showing posts with label Timezone. Show all posts

Wednesday, December 1, 2010

Time offsets to UTC in MySQL

The offset from UTC is given in the format ±[hh]:[mm], ±[hh][mm], or ±[hh]. It is appended to the time. The offset from UTC changes with daylight saving time, e.g. a time offset in Chicago, would be "-06:00" for the winter (Central Standard Time) and "-05:00" for the summer (Central Daylight Time).

The following times all refer to the same moment: "18:30Z", "22:30+04", "1130-0700", and "15:00-03:30". Nautical time zone letters are not used with the exception of Z. To calculate UTC time one has to subtract the offset from the local time, e.g. for "15:00-03:30" do 15:00 − (−03:30) to get 18:30 UTC.

The offset can also be used in the case where the UTC time is known, but the local offset is not. In this case the offset is "-00:00", which is semantically different from "Z" or "+00:00", as these imply that UTC is the preferred reference point for those times.

SELECT CONVERT_TZ('2004-01-01 11:30:00','-07:00','+00:00');