Function parse_date 

pub fn parse_date(input: &str) -> IResult<&str, DateTime>

Parse an AIMX date literal.

Tries, in order:

• YYYY-MM-DD[ T]HH:MM:SS[.sss]Z
• YYYY-MM-DD[ T]HH:MM:SS[.sss]
• YYYY-MM-DD.

Returns remaining input and the parsed [DateTime].