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Timing

Working with times & time zones 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 way, 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

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 class that used to set the clock kind.

Example: Use UTC Clock

Configure<AbpClockOptions>(options =>
{
    options.Kind = DateTimeKind.Utc;
});

Write this inside the ConfigureServices method of your module.

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:

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.
Working with DateTime objects on JSON deserialization.

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.

Time Zones

This section covers the ABP Framework infrastructure related to managing time zones.

TimeZone Setting

ABP Framework defines a setting, named Abp.Timing.Timezone, that can be used to set and get the time zone for a user, tenant or globally for the application. The default value is UTC.

See the setting documentation to learn more about the setting system.

ITimezoneProvider

ITimezoneProvider is a service to simple convert Windows Time Zone Id values to Iana Time Zone Name values and vice verse. It also provides methods to get list of these time zones and get a TimeZoneInfo with a given name.

It has been implemented using the TimeZoneConverter library.

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