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datetimeinvalidlocalformat-mda.md

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title description ms.date helpviewer_keywords ms.assetid
dateTimeInvalidLocalFormat MDA
Review the dateTimeInvalidLocalFormat managed debugging assistant (MDA), which is activated when a UTC-stored DateTime value gets a local-only DateTime format.
03/30/2017
dates [.NET Framework], formatting
invalid date time local format
invalid local formats
MDAs (managed debugging assistants), invalid local formats
managed debugging assistants (MDAs), invalid local formats
dateTimeInvalidLocalFormat MDA
date formatting
time formatting
UTC formatting
c4a942bb-2651-4b65-8718-809f892a0659

dateTimeInvalidLocalFormat MDA

The dateTimeInvalidLocalFormat MDA is activated when a xref:System.DateTime instance that is stored as a Universal Coordinated Time (UTC) is formatted using a format that is intended to be used only for local xref:System.DateTime instances. This MDA is not activated for unspecified or default xref:System.DateTime instances.

Symptom

An application is manually serializing a UTC xref:System.DateTime instance using a local format:

DateTime myDateTime = DateTime.UtcNow;  
Serialize(myDateTime.ToString("yyyy-MM-dd'T'HH:mm:ss.fffffffzzz"));

Cause

The 'z' format for the xref:System.DateTime.ToString%2A?displayProperty=nameWithType method includes the local time zone offset, for example, "+10:00" for Sydney time. As such, it will only produce a meaningful result if the value of the xref:System.DateTime is local. If the value is UTC time, xref:System.DateTime.ToString%2A?displayProperty=nameWithType includes the local time zone offset, but it does not display or adjust the time zone specifier.

Resolution

UTC xref:System.DateTime instances should be formatted in a way that indicates that they are UTC. The recommended format for UTC times to use a 'Z' to denote UTC time:

DateTime myDateTime = DateTime.UtcNow;  
Serialize(myDateTime.ToString("yyyy-MM-dd'T'HH:mm:ss.fffffffZ"));

There is also an "o" format that serializes a xref:System.DateTime making use of the xref:System.DateTime.Kind%2A property that serializes correctly regardless of whether the instance is local, UTC, or unspecified:

DateTime myDateTime = DateTime.UtcNow;  
Serialize(myDateTime.ToString("o"));

Effect on the Runtime

This MDA does not affect the runtime.

Output

There is no special output as a result of this MDA activating., However, the call stack can be used to determine the location of the xref:System.DateTime.ToString%2A call that activated the MDA.

Configuration

<mdaConfig>  
  <assistants>  
    <dateTimeInvalidLocalFormat />  
  </assistants>  
</mdaConfig>

Example

Consider an application that is indirectly serializing a UTC xref:System.DateTime value by using the xref:System.Xml.XmlConvert or xref:System.Data.DataSet class, in the following manner.

DateTime myDateTime = DateTime.UtcNow;  
String serialized = XMLConvert.ToString(myDateTime);

The xref:System.Xml.XmlConvert and xref:System.Data.DataSet serializations use local formats for serialization by default. Additional options are required to serialize other kinds of xref:System.DateTime values, such as UTC.

For this specific example, pass in XmlDateTimeSerializationMode.RoundtripKind to the ToString call on XmlConvert. This serializes the data as a UTC time.

If using a xref:System.Data.DataSet, set the xref:System.Data.DataColumn.DateTimeMode%2A property on the xref:System.Data.DataColumn object to xref:System.Data.DataSetDateTime.Utc.

DateTime myDateTime = DateTime.UtcNow;  
String serialized = XmlConvert.ToString(myDateTime,
    XmlDateTimeSerializationMode.RoundtripKind);

See also