Document Weekday Ordinals about cron

[sbditto85]

I would argue that it should be changed to be 0-6 or have a configuration to pick between 0-6 or 1-7 as right now if we wanted to use this crate we'd need to fork it and change it to 0-6. Otherwise, the crate looks great!

[zslayton]

See also: #37. Sunday=1 was taken from the Quartz service.

Maybe this should be documented somewhere.

+1.

I would argue that it should be changed to be 0-6

I can't do this as there are folks using it for parsing Quartz's flavor of cron expressions.

or have a configuration to pick between 0-6 or 1-7

This would be great! There are other settings that would be nice to have, too. Off the top of my head:

• Named ordinal support for other languages (Mon,Tues,Wed in English -> Lun,Mar,Mer in French)
• Some locales start the week on Monday, not Sunday.
• 5-field expressions in which the leftmost field is meant to be a year instead of the rightmost being seconds.

I'd like to have a builder API that lets folks opt into these settings. Exposing a day-of-week ordinals option would be a good place to start. If anyone is interested in implementing that, let me know and we can sketch out what the API should look like.

[hce]

Hello, I'd also like to say this is a great crate! :-)
I'm also here because of the weekday numbering scheme; I was expecting a standard unix scheme where 0 and 7 means sunday, while 1 means monday, etc. It would be great if this behavior could be enabled by some option.