Update README.md

README.md

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 This code is specifically for my ITS1A clock, which is documented here: https://www.nixies.us/projects/its1a-clock/
 
+The current version uses NTP for time synchronization and can handle daylight-savings time. The format is defined [here](https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html). There is a full list of strings defined [here](https://github.com/nayarsystems/posix_tz_db/blob/master/zones.csv).
+
+Here are some examples:
+
+| Location | Value |
+| ------------- | ------------- |
+| US Central | CST6CDT,M3.2.0,M11.1.0 |
+| US Eastern | EST5EDT,M3.2.0,M11.1.0 |
+| US Mountain | MST7MDT,M3.2.0,M11.1.0 |
+| US Pacific | PST8PDT,M3.2.0,M11.1.0 |
+| UK | GMT0BST,M3.5.0/1,M10.5.0 |
+| Ireland | IST-1GMT0,M10.5.0,M3.5.0/1 |
+| Central Europe | CET-1CEST,M3.5.0,M10.5.0/3 |
+| Eastern Europe | EET-2EEST,M3.5.0/3,M10.5.0/4 |
+| Japan | JST-9 |
+| Australia/Brisbane | AEST-10 |
+| Australia/Perth | AWST-8 |
+| Australia/Adelaide | ACST-9:30ACDT,M10.1.0,M4.1.0/3 |
+| Australia/Sydney | AEST-10AEDT,M10.1.0,M4.1.0/3 |