Translations:Help:TemplateData/615/en

The $1 value is intended for a date in the YYYY-MM-DD (ISO 8601) format; for example, 2014-05-22. The TemplateData manual also designates it as being intended for ISO 8601 date–time combinations, such as 2014-05-22T16:01:12Z", but in practice no major editing interface as of February 2020 uses it in this fashion, and almost all major Wikimedia template parameters take dates and times separately.