It's pretty horrible. Apart from being hard to read (why pick an uppercase later that looks similar to numerals?), it only works for full dates or times or dat

It's pretty horrible. Apart from being hard to read (why pick an uppercase later that looks similar to numerals?), it only works for full dates or times or datetimes. You can't have literals for just years, or just hours, or just a a particular month. Even 10:20 is ambigious -- is that twenty past 10 (am), or 10 minutes 20 seconds past the hour, or a duration (iso also covers durations, but they are weird and clunky)? Compare 2020-7-29T19:45 to Chinese style: 2020年7月29日19時45分 Easier to read and you can pick any subset of components unambiguously.