Silent failure on conversion from string to DateTime about dates.jl

[quinnj]

Yeah, that is tricky. The whole providing-a-default format string has pretty much only led to problems, at least for DateTime. Maybe we get rid of it for DateTime and make the user supply the format string. Dates are much less prone to error, so maybe we can keep it there.

[danluu]

Yeah, I'd definitely prefer no default format over "random" silent failures. I haven't done ruby for at least 6 years, but my recollection was that their DateTime would often just magically get the right answer. That's probably pretty complicated and still somewhat error prone, though.