Function FLEncoder_WriteDateString 

pub unsafe extern "C" fn FLEncoder_WriteDateString(
    encoder: FLEncoder,
    ts: FLTimestamp,
    asUTC: bool,
) -> bool

Writes a timestamp to an encoder, as an ISO-8601 date string. @note Since neither Fleece nor JSON have a ‘Date’ type, the encoded string has no metadata that distinguishes it as a date. It’s just a string.) @param encoder The encoder to write to. @param ts The timestamp (milliseconds since Unix epoch 1-1-1970). @param asUTC If true, date is written in UTC (GMT); if false, with the local timezone. @return True on success, false on error.