Change default of SerializationFeature.WRITE_DATES_AS_TIMESTAMPS to false in 3.0

(note: part of proposed changes via https://github.com/FasterXML/jackson-future-ideas/wiki/JSTEP-2)

It seems that the default of writing basic Date/Time values as numeric timestamps is something that should be changed: while this is more efficient than the alternative of writing Date/Time value as Strings, most users expect Strings, and most frameworks seem to change the default.

So the proposal is to change the default accordingly.

Change has been approved: we can proceed with change!

Fix tests post FasterXML#4845

[Jackson3.0] Fix #4845: change `SerializationFeature.WRITE_DATES_AS_T…

Defaults have been changed for 3.0.0-rc1.

Is there some place that explicitly lists which date/time classes from the JDK are affected, and how?

I went through various pages linked from this discussion, but could not find anything definitive.

@soc

@soc this is configurable. If you don't like the setting default, you can change it.

Both liking/disliking as well as configuring a setting requires understanding what the setting does, which is the exact topic of my original question.

and long closed issues are not the place to suddenly start a discussion. Open a GitHub discussion.

What discussion?

@soc

@soc https://github.com/FasterXML/jackson-databind/discussions - anyone can open discussions there

The Javadoc on these feature is quite detailed. I don't see how we could be much more specific.

jackson-databind/src/main/java/tools/jackson/databind/cfg/DateTimeFeature.java

Lines 148 to 172 in 9b2adbf

    
                * Feature that determines whether Date (and date/time) values 
        
                * (and Date-based things like {@link java.util.Calendar}s) are to be 
        
                * serialized as numeric time stamps ({@code true}), 
        
                * or as textual representation ({@code false}). 
        
                * If textual representation is used, the actual format depends on configuration 
        
                * settings including global defaults and possible per-type and/or per-property 
        
                * {@code @JsonFormat} annotation overrides. 
        
                *<p> 
        
                * For "classic" JDK date types ({@link java.util.Date}, {@link java.util.Calendar}) 
        
                * the default formatting is provided by {@link tools.jackson.databind.util.StdDateFormat}, 
        
                * and corresponds to format String of "yyyy-MM-dd'T'HH:mm:ss.SSSX" 
        
                * (see {@link java.text.DateFormat} for details of format Strings). 
        
                * For Java 8 ({@code java.time.*}) and Joda Date-time textual format 
        
                * configuration differs, but this feature is still used as global 
        
                * default when choosing between numeric time stamps and textual representation. 
        
                *<p> 
        
                * Note: whether {@link java.util.Map} keys are serialized as Strings 
        
                * or not is controlled using {@link #WRITE_DATE_KEYS_AS_TIMESTAMPS} instead of 
        
                * this feature. 
        
                *<p> 
        
                * Feature used to be one of {@link tools.jackson.databind.SerializationFeature}s 
        
                * in Jackson 2.x but was moved here in 3.0. 
        
                *<p> 
        
                * Feature is disabled by default as of Jackson 3.0 (in 2.x it was enabled), 
        
                * so that date/time are by default serialized as textual values NOT timestamps.

Jackson 3:

 WRITE_DATES_AS_TIMESTAMPS   |          true          |          false
---------------------------------------------------------------------------------------
 java.util.Date              | "1596105045000"        | "\"2020-07-30T10:30:45.000Z\""
 java.util.GregorianCalendar | "1596105045000"        | "\"2020-07-30T10:30:45.000Z\""
 java.time.Instant           | "1596112245.000000000" | "\"2020-07-30T12:30:45Z\""
 java.time.LocalDateTime     | "[2020,7,30,12,30,45]" | "\"2020-07-30T12:30:45\""
 etc.

Jackson 2:

 WRITE_DATES_AS_TIMESTAMPS   |          true          |          false
---------------------------------------------------------------------------------------
 java.util.Date              | "1596105045000"        | "\"2020-07-30T10:30:45.000+00:00\""
 java.util.GregorianCalendar | "1596105045000"        | "\"2020-07-30T10:30:45.000+00:00\""
 java.time.Instant           | "1596112245.000000000" | "\"2020-07-30T12:30:45Z\""
 java.time.LocalDateTime     | "[2020,7,30,12,30,45]" | "\"2020-07-30T12:30:45\""
 etc.

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Change default of `SerializationFeature.WRITE_DATES_AS_TIMESTAMPS` to `false` in 3.0 #4845

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	* Feature that determines whether Date (and date/time) values
	* (and Date-based things like {@link java.util.Calendar}s) are to be
	* serialized as numeric time stamps ({@code true}),
	* or as textual representation ({@code false}).
	* If textual representation is used, the actual format depends on configuration
	* settings including global defaults and possible per-type and/or per-property
	* {@code @JsonFormat} annotation overrides.
	*<p>
	* For "classic" JDK date types ({@link java.util.Date}, {@link java.util.Calendar})
	* the default formatting is provided by {@link tools.jackson.databind.util.StdDateFormat},
	* and corresponds to format String of "yyyy-MM-dd'T'HH:mm:ss.SSSX"
	* (see {@link java.text.DateFormat} for details of format Strings).
	* For Java 8 ({@code java.time.*}) and Joda Date-time textual format
	* configuration differs, but this feature is still used as global
	* default when choosing between numeric time stamps and textual representation.
	*<p>
	* Note: whether {@link java.util.Map} keys are serialized as Strings
	* or not is controlled using {@link #WRITE_DATE_KEYS_AS_TIMESTAMPS} instead of
	* this feature.
	*<p>
	* Feature used to be one of {@link tools.jackson.databind.SerializationFeature}s
	* in Jackson 2.x but was moved here in 3.0.
	*<p>
	* Feature is disabled by default as of Jackson 3.0 (in 2.x it was enabled),
	* so that date/time are by default serialized as textual values NOT timestamps.

Change default of SerializationFeature.WRITE_DATES_AS_TIMESTAMPS to false in 3.0 #4845

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cowtowncoder commented on Jan 30, 2025

cowtowncoder commented on Feb 7, 2025

soc commented on Jul 22, 2026

pjfanning commented on Jul 22, 2026

soc commented on Jul 22, 2026

pjfanning commented on Jul 22, 2026

soc commented on Jul 22, 2026

pjfanning commented on Jul 22, 2026

pjfanning commented on Jul 22, 2026

soc commented on Jul 22, 2026

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Change default of `SerializationFeature.WRITE_DATES_AS_TIMESTAMPS` to `false` in 3.0 #4845