Type alias ISODayOfMonth

ISODayOfMonth: `0${Exclude<Digit, 0>}` | `${1 | 2}${Digit}` | `3${Enumerate<2>}`

ISO day of month value ("01" to "31").

const day01: ISODayOfMonth = "01";
const day15: ISODayOfMonth = "15";
const day31: ISODayOfMonth = "31";