README.md in ziptz-5.1.0 vs README.md in ziptz-5.1.1

- old
+ new

@@ -4,10 +4,10 @@
 [![Total Downloads](https://img.shields.io/gem/dt/ziptz.svg)](https://rubygems.org/gems/ziptz/)
 [![License](https://img.shields.io/github/license/infused/ziptz.svg)](https://github.com/infused/ziptz)
 
 Get time zone, daylight saving time, and base offset for any US ZIP code.
 
-<i>ZIP codes are up to date as of <b>December 2023</b>.</i>
+<i>ZIP codes are up to date as of <b>May 2024</b>.</i>
 
 ## Compatibility
 
 Ziptz is tested to work with the following versions of Ruby:
 