convert a date-time-like string to a valid ISO 8601-compatible date string
for direct output or further processing via chrono
If date_opts is None, the function will attempt to guess the date order with bias towards YMD and DMY in case of ambiguity
For best performance, provide the date order and splitter
convert a date-time-like string to a valid ISO 8601-compatible string
dt: the date-time string
separator: the separator between the date and time parts
add_z: whether to add ‘Z’ timezone indicator
convert a date-time-like string to a valid ISO 8601-compatible date-time string
for direct output or further processing via chrono
Assume all input dates conforms to the ISO 8601 order, even if incomplete. All guessing is short-circuited
This is compatible with original function in julian_day_converter
Convert a ISO YMD date-like string to a NaiveDate
It assumes Y-M-D order and a hyphen as the splitter, but can accommodate missing month or day components