---
title: "Event Sourcing: the not-so-simple bi-temporal basics"
url: https://daily.dev/posts/event-sourcing-the-not-so-simple-bi-temporal-basics-t4ntaclgn
source_url: https://www.planetgeek.ch/2026/06/02/event-sourcing-the-not-so-simple-bi-temporal-basics
type: article
source: "We Are .NET"
published: 2026-06-02T08:12:34.017Z
updated: 2026-06-02T08:12:58.704Z
tags: ["architecture", ".net", "domain-driven-design"]
reading_time: 7
upvotes: 0
comments: 0
language: en
---

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# Event Sourcing: the not-so-simple bi-temporal basics

**[We Are .NET](https://daily.dev/sources/wearedotnet)** · 7 min read · 0 upvotes · 0 comments

## Summary

Part eight of an event sourcing series covering bi-temporal event sourcing fundamentals. Explains why two timestamps are needed — an application timestamp (when the event entered the system) and an effective timestamp (when it takes effect) — enabling queries against past, present, or future states. Introduces the concept of timelines as a projection mechanism built from bi-temporal event streams, covering sort ordering (effective time first, application time as tiebreaker), granularity differences between the two timestamps, and a concrete F# code example using a TimelineProjector with organisation chart events.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.planetgeek.ch/2026/06/02/event-sourcing-the-not-so-simple-bi-temporal-basics>

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Tags: [#architecture](https://daily.dev/tags/architecture), [#.net](https://daily.dev/tags/.net), [#domain-driven-design](https://daily.dev/tags/domain-driven-design)

[View this post on daily.dev](https://daily.dev/posts/event-sourcing-the-not-so-simple-bi-temporal-basics-t4ntaclgn)