Document default for MVC and WebFlux date and time formatting

Closes gh-30041

spring-boot-project/spring-boot-docs/src/docs/asciidoc/web/reactive.adoc

@@ -46,6 +46,28 @@ If you want to take complete control of Spring WebFlux, you can add your own `@C
 
 
 
+[[web.reactive.webflux.conversion-service]]
+==== Spring WebFlux Conversion Service
+If you want to customize the `ConversionService` used by Spring WebFlux, you can provide a `WebFluxConfigurer` bean with an `addFormatters` method.
+
+Conversion can also be customized using the `spring.webflux.format.*` configuration properties.
+When not configured, the following defaults are used:
+
+|===
+|Property |`DateTimeFormatter`
+
+|configprop:spring.webflux.format.date[]
+|`ofLocalizedDate(FormatStyle.SHORT)`
+
+|configprop:spring.webflux.format.time[]
+|`ofLocalizedTime(FormatStyle.SHORT)`
+
+|configprop:spring.webflux.format.date-time[]
+|`ofLocalizedDateTime(FormatStyle.SHORT)`
+|===
+
+
+
 [[web.reactive.webflux.httpcodecs]]
 ==== HTTP Codecs with HttpMessageReaders and HttpMessageWriters
 Spring WebFlux uses the `HttpMessageReader` and `HttpMessageWriter` interfaces to convert HTTP requests and responses.

spring-boot-project/spring-boot-docs/src/docs/asciidoc/web/servlet.adoc

@@ -48,14 +48,31 @@ If you want to provide custom instances of `RequestMappingHandlerMapping`, `Requ
 
 If you want to take complete control of Spring MVC, you can add your own `@Configuration` annotated with `@EnableWebMvc`, or alternatively add your own `@Configuration`-annotated `DelegatingWebMvcConfiguration` as described in the Javadoc of `@EnableWebMvc`.
 
-[NOTE]
+
-====
+
+[[web.servlet.spring-mvc.conversion-service]]
+==== Spring MVC Conversion Service
 Spring MVC uses a different `ConversionService` to the one used to convert values from your `application.properties` or `application.yaml` file.
 It means that `Period`, `Duration` and `DataSize` converters are not available and that `@DurationUnit` and `@DataSizeUnit` annotations will be ignored.
 
 If you want to customize the `ConversionService` used by Spring MVC, you can provide a `WebMvcConfigurer` bean with an `addFormatters` method.
 From this method you can register any converter that you like, or you can delegate to the static methods available on `ApplicationConversionService`.
-====
+
+Conversion can also be customized using the `spring.mvc.format.*` configuration properties.
+When not configured, the following defaults are used:
+
+|===
+|Property |`DateTimeFormatter`
+
+|configprop:spring.mvc.format.date[]
+|`ofLocalizedDate(FormatStyle.SHORT)`
+
+|configprop:spring.mvc.format.time[]
+|`ofLocalizedTime(FormatStyle.SHORT)`
+
+|configprop:spring.mvc.format.date-time[]
+|`ofLocalizedDateTime(FormatStyle.SHORT)`
+|===