fix typos in release dates (#377)

Author: Jericho

plugin-gradle/CHANGES.md

@@ -2,7 +2,7 @@
 
 ### Version 3.21.0-SNAPSHOT - TBD ([javadoc](https://diffplug.github.io/spotless/javadoc/snapshot/), [snapshot](https://oss.sonatype.org/content/repositories/snapshots/com/diffplug/spotless/spotless-plugin-gradle/))
 
-### Version 3.20.0 - March 11th 2018 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.20.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.20.0))
+### Version 3.20.0 - March 11th 2019 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.20.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.20.0))
 
 * Made npm package versions of [`prettier`](https://prettier.io/) and [`tsfmt`](https://github.com/vvakame/typescript-formatter) (and its internal packages) configurable. ([#363](https://github.com/diffplug/spotless/pull/363))
   * Updated default npm package version of `prettier` from 1.13.4 to 1.16.4
@@ -14,14 +14,14 @@
 * Default behavior of XML formatter changed to ignore external URIs ([#369](https://github.com/diffplug/spotless/issues/369)).
   * **WARNING RESOLVED: By default, xml formatter no longer downloads external entities. You can opt-in to resolve external entities by setting resolveExternalURI to true. However, if you do opt-in, be sure that all external entities are referenced over https and not http, or you may be vulnerable to XXE attacks.**
 
-### Version 3.19.0 - March 11th 2018 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.19.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.19.0))
+### Version 3.19.0 - March 11th 2019 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.19.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.19.0))
 
 **WARNING: xml formatter in this version may be vulnerable to XXE attacks, fixed in 3.20.0 (see [#358](https://github.com/diffplug/spotless/issues/358)).**
 
 * Security fix: Updated groovy, c/c++, and eclipse WTP formatters so that they download their source jars securely using `https` rather than `http` ([#360](https://github.com/diffplug/spotless/issues/360)).
 * Updated default eclipse-jdt from 4.9.0 to 4.10.0 ([#368](https://github.com/diffplug/spotless/pull/368))
 
-### Version 3.18.0 - February 11th 2018 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.18.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.18.0))
+### Version 3.18.0 - February 11th 2019 ([javadoc](https://diffplug.github.io/spotless/javadoc/spotless-plugin-gradle/3.18.0/), [jcenter](https://bintray.com/diffplug/opensource/spotless-plugin-gradle/3.18.0))
 
 **WARNING: xml formatter in this version may be vulnerable to XXE attacks, fixed in 3.20.0 (see [#358](https://github.com/diffplug/spotless/issues/358)).**