00:23:22:21:20:19:18:17:16:15:14:13:12:11:10:09:08:07:06:05:04:03:02:01:5432109:8:7:6:5:4:3:2:1:0:5432109876543210

An experimental clock with only CSS, calibrated by PHP. It seems synced with UTC's reality. Math saved me from experimenting repeatedly with the leftmost digits. Feel free to view the source, go big, or use the TimeZone feature