10/10 - lemm.ee

Nothing beats ISO 8601, YYYY-MM-DD
RFC 3339! ISO 8601 has way too many weird formats that are allowed like today would be 2023-W41-2. See for example here.
RFC 3339 vs ISO 8601

Comparison between RFC 3339 and ISO 8601 date formats

Whoa, thatโ€™s a cool website!
Itโ€™s really pleasing seeing the seconds all change in unison!