If you input a date in the URL bar of Firefox1, it gets rewritten into an ip if the year is less than 65536. Actually, every date-like string gets rewritten if the day and month are less than 256 and the year is less than 65536.

The reason is that Firefox uses this string as an ip adress: The day and month are the first two octets, the last number gets paddded with zeros, until it is 16 bits long, and converted into the last octets.

One example: 24.11.2021 -> 24.11.7.229.

   24       11          2021
   11000     1011      11111100101
00011000 00001011 0000011111100101

00011000 00001011 00000111 11100101
   24       11        7       229

The last number also gets converted if it is less than 256, e.g. 24.11.21 -> 24.11.0.21.

   24       11            21
   11000     1011            10101
00011000 00001011 0000000000010101

00011000 00001011 00000000 00010101
   24       11        0       21

The behaviour is known and tracked in Bug #1602034 but it doesn’t look like this behaviour will get changed. It got introduced in Bug #1067168 in response to a comment.

Chrome only accepts properly formatted ip adresses in dot-decimal notation, however, both Firefox and Chrome interpret a number (with a http:// prefix) as an ip adress as well:

http://24112021 -> http://1.111.235.149/

             24112021
       1 01101111 11101011 10010101
00000001 01101111 11101011 10010101
    1       111      235      149

  1. I am using Firefox 94.0.2 right now. ↩︎