From 994a0fa777c07105bb53ea9c25011538c521e152 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Halil=20=C4=B0brahim=20Kalkan?= <hi_kalkan@yahoo.com>
Date: Fri, 12 Jun 2020 16:18:53 +0300
Subject: [PATCH] Complete IClock part of the Timing document.

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+# JSON
+
+TODO
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 # Timing
 
-TODO
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+Working with times & [time zones](https://en.wikipedia.org/wiki/Time_zone) is always tricky, especially if you need to build a **global system** that is used by users in **different time zones**.
+
+ABP provides a basic infrastructure to make it easy and handle automatically wherever possible. This document covers the ABP Framework services and systems related to time and time zones.
+
+> If you are creating a local application that runs in a single time zone region, you may not need all these systems. But even in this case, it is suggested to use the `IClock` service introduced in this document.
+
+## IClock
+
+`DateTime.Now` returns a `DateTime` object with the **local date & time of the server**. A `DateTime` object **doesn't store the time zone information**. So, you can not know the **absolute date & time** stored in this object. You can only make **assumptions**, like assuming that it was created in UTC+05 time zone. The things especially gets complicated when you save this value to a database and read later, or send it to a client in a **different time zone**.
+
+One solution to this problem is always use `DateTime.UtcNow` and assume all `DateTime` objects as UTC time. In this was, you can convert it to the time zone of the target client when needed.
+
+`IClock` provides an abstraction while getting the current time, so you can control the kind of the date time (UTC or local) in a single point in your application.
+
+**Example: Getting the current time**
+
+````csharp
+using Volo.Abp.DependencyInjection;
+using Volo.Abp.Timing;
+
+namespace AbpDemo
+{
+    public class MyService : ITransientDependency
+    {
+        private readonly IClock _clock;
+
+        public MyService(IClock clock)
+        {
+            _clock = clock;
+        }
+
+        public void Foo()
+        {
+            //Get the current time!
+            var now = _clock.Now;
+        }
+    }
+}
+````
+
+* Inject the `IClock` service when you need to get the current time. Common base classes (like ApplicationService) already injects it and provides as a base property - so, you can directly use as `Clock`.
+* Use the `Now` property to get the current time.
+
+> Most of the times, `IClock` is the only service you need to know and use in your application.
+
+### Clock Options
+
+`AbpClockOptions` is the [options](Options.md) class that used to set the clock kind.
+
+**Example: Use UTC Clock**
+
+````csharp
+Configure<AbpClockOptions>(options =>
+{
+    options.Kind = DateTimeKind.Utc;
+});
+````
+
+Write this inside the `ConfigureServices` method of your [module](Module-Development-Basics.md).
+
+> Default `Kind` is `Unspecified`, that actually make the Clock as it doesn't exists at all. Either make it `Utc` or `Local` if you want to get benefit of the Clock system.
+
+### DateTime Normalization
+
+Other important function of the `IClock` is to normalize `DateTime` objects.
+
+**Example usage:**
+
+````csharp
+DateTime dateTime = ...; //Get from somewhere
+var normalizedDateTime = Clock.Normalize(dateTime)
+````
+
+`Normalize` method works as described below:
+
+* Converts the given `DateTime` to the UTC (by using the `DateTime.ToUniversalTime()` method) if current Clock is UTC and given `DateTime` is local.
+* Converts the given `DateTime` to the local (by using the `DateTime.ToLocalTime()` method) if current Clock is local and given `DateTime` is UTC.
+* Sets `Kind` of the given `DateTime` (using the `DateTime.SpecifyKind(...)` method) to the `Kind` of the current Clock if given `DateTime`'s `Kind` is `Unspecified`.
+
+`Normalize` method is used by the ABP Framework when the it gets a `DateTime` that is not created by `IClock.Now` and may not be compatible with the current Clock type. Examples;
+
+* `DateTime` type binding in the ASP.NET Core MVC model binding.
+* Saving data to and reading data from database via [Entity Framework Core](Entity-Framework-Core.md).
+* Working with `DateTime` objects on [JSON deserialization](Json.md).
+
+#### DisableDateTimeNormalization Attribute
+
+`DisableDateTimeNormalization` attribute can be used to disable the normalization operation for desired classes or properties.
+
+### Other IClock Properties
+
+In addition to the `Now`, `IClock` service has the following properties:
+
+* `Kind`: Returns a `DateTimeKind` for the currently used clock type (`DateTimeKind.Utc`, `DateTimeKind.Local` or `DateTimeKind.Unspecified`).
+* `SupportsMultipleTimezone`: Returns `true` if currently used clock is UTC.
+
+### 
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