I remember when I was pursuing a computer diploma, I developed a Sri Lanka identity card decoder that could extract your birthday and gender from your national identity card number. Initially, I developed it using GWBASIC, which is a rather old programming language, and I aspired to rewrite it in C# and PHP. The program is quite straightforward, and you can test it with your own NIC. (Updated to the New NIC number format as well.)
https://www.tilantha.com/resources/sri-lanka-national-identity-card-decoder/