On Thu, Jul 13, 2006 at 04:35:20PM -0700, Antimon wrote: > Hi, > I'm working on a web project with pgsql, i did use mysql before and > stored epoch in database so i'm not familiar with these datatypes. > > What i wanna ask is, if i don't need to display timestamps in different > timezones, shall i use timestamptz anyway? I mean, i'm gonna need > timestamp columns on some tables for internal calculations and stuff > like delaying actions, adding a row with a timestamp of 10 minutes > later and check for them every minute, fetch elapsed ones and process, > not to display them to users. The choice between timezone and timezonetz depends on what you're using it for: timestamptz identifies a specific point in time. It will be adjusted before output to reflect the timezone of the person selecting it. timestamp is a representation of a wall clock. The difference is easy to show when you're dealing with daylight savings times. In central european time the date '2006-03-26 02:30:00' doesn't exist, yet you can store it in a timestamp, but not in a timestamptz. For timestamptz, the time jumps from 2006-03-26 02:00:00 +0100 to 2006-03-26 03:00:00 +0200. And calculations take this into account. Similarly when daylight savings ends, a timestamptz can handle the fact that 2:30 am occurs twice, whereas timestamp won't. You can use the X AT TIME ZONE Y construct to convert between the two. Hope this helps, -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
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