![]() NET type: if a function accepts a DateTime, which Kind should you pass in? What happens when you compare a UTC DateTime with an Unspecified one? (The answer is that the timestamps will be compared disregarding the Kind, which I can’t imagine can produce fruitful results in any sane application). One problematic aspect of DateTime is that these very different concepts are represented via the same. NET is running, and Unspecified is, well, not very specified. NET timestamp arsenal includes two main types: DateTime and DateTimeOffset.ĭateTime unsurprisingly contains a date and a time, but also a Kind property which can be Utc, Local or Unspecified: Utc is pretty self-explanatory, Local means a timestamp in the timezone of the machine where. NET has some basic flaws in this area which have been with us since the beginning of time, and cannot be corrected without introducing unacceptable breaking changes. NET situation around timestamps is… not pretty…. However, fiddling around with your connection’s TimeZone and depending on your database to do timezone conversions usually isn’t a practical way to do things - you typically want to store and retrieve UTC timestamps from your database, and do any conversions to/from local timezones in your application, when interacting with users.NET timestamps When converting a timestamp into a timestamptz (remember: the latter means “UTC”), PostgreSQL will treat your timestamp as a local timestamp, and convert it to UTC based on the connection’s current TimeZone. PostgreSQL does have a TimeZone connection state parameter, which defines the “local time zone” of the connection it’s defined in your PostgreSQL configuration by default, and can be changed in your connection. It’s really important to understand that this does not represent a specific point in time unless coupled with some time zone: the same date/time combination corresponds to different universal instances in different time zones. The other type - timestamp - can be used to store a timestamp whose time zone is unknown, implicit or assumed to be local. In the relatively rarer cases where you need to store the time zone along with a timestamp, a separate column must be used alongside your timestamp column, typically holding a string representation of the timezone (e.g. This is sometimes called doing “UTC everywhere”, and it tends to work well as a default pattern. For example, when recording the time a transaction took place, you typically store a UTC timestamp, and then display it in the user’s local time zone, as reported by their web browser this allows you to show the same timestamp to multiple users, each in their own time zone, and also to support the fact that users may be in one time zone today, and in another tomorrow. ![]() What timestamptz is good for, is storing and interacting with UTC timestamps, or globally agreed-upon points in time, where the time zone does not matter. In this sense, timestamptz is different from the SQL Server datetimeoffset type (but see note below on why offsets may be a bad idea). timestamptz is perhaps the worst-named type in the world: it does not, in fact, store a time zone in the database, but rather a UTC timestamp that causes lots of confusion from users expecting to persist a full timezone-aware timestamp to PostgreSQL. ![]() Like with most things, PostgreSQL conforms to the SQL standard when it comes to timestamps ( full docs): it has a timestamp without time zone and a timestamp with time zone type (the shorter aliases are timestamp and timestamptz). This post gives the context for these changes, going over the timestamp types on both sides and the problems in mapping them. NET and PostgreSQL - most applications will need to react to this (although a compatibility flag exists). ![]() ![]() Npgsql 6.0 contains some significant changes to how timestamps are mapped between. INTERESTED IN TIMESTAMPS? SEE ALSO When “UTC everywhere” isn’t enough - storing time zones in PostgreSQL and SQL Server ![]()
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