--- title: All Your GUCs in a Row: DateStyle | daily.dev description: PostgreSQL's DateStyle GUC is actually two settings in one: an output format (ISO, Postgres, SQL, German) and an input ordering for ambiguous dates (MDY, DMY,... canonical: https://daily.dev/posts/all-your-gucs-in-a-row-datestyle-knzjuidde twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: All Your GUCs in a Row: DateStyle | daily.dev og:description: PostgreSQL's DateStyle GUC is actually two settings in one: an output format (ISO, Postgres, SQL, German) and an input ordering for ambiguous dates (MDY, DMY,... og:url: https://daily.dev/posts/all-your-gucs-in-a-row-datestyle-knzjuidde og:image: https://api.daily.dev/og/posts/KnZjuIdDE.png og:image:alt: All Your GUCs in a Row: DateStyle og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # All Your GUCs in a Row: DateStyle **[Planet PostgreSQL](https://daily.dev/sources/planet-postgresql)** · 3 min read · 0 upvotes · 0 comments ## Summary PostgreSQL's DateStyle GUC is actually two settings in one: an output format (ISO, Postgres, SQL, German) and an input ordering for ambiguous dates (MDY, DMY, YMD). The common confusion is trying to set MDY as an output format when it only affects input parsing. The recommendation is to always use ISO output — it's sortable, locale-independent, and unambiguous — and use to_char() for any application-specific formatting needs. A notable gotcha: initdb may write a DateStyle based on the cluster's lc_time locale, causing different clusters to interpret ambiguous dates differently. ## Full article daily.dev links to this article rather than hosting it. 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