Tinderbox lets you set negative years in Dates but doesn’t - as yet - display them as such, except in Timeline view.
As regards your attempt with dates dating from year zero, there is no year 0000. The dates will run from 31 Dec -0001 to 1 Jan 0001.
Negative dates are best regarded as experimental and can only be used in Timeline view because there isn’t yet any way to display negative (BCE) dates as such other than setting your OS [sic] settings to show an AD/BC suffix to dates. Likely negative date support will improve but as to when I’ve no idea. If you’ve specific requests in this area, I’d email them to Eastgate.
For fantasy dates, I’d start at 1/1/0001 and work up. Note that for years with less than 3 digits you need to supply a four digit value, i.e. 0001 or 0010 not 1 or 10. Frankly I’d use 4 digits for 3 digits years too (0100 not 100) as that way you use the same ‘rule’ for all.
[Edit!]
To enter negative dates via key attributes, you must set your OS ‘short’ date form to use a space after the year and then the ‘AD’ era tag. Then use " BC" after the date, e.g. “1/3/0004 BC” - though this doesn’t work reliably for me. This does:
- make a stamp with this code: $StartDate.year = ($StartDate.year-(2*$StartDate.year)-1)
- set your $StatDate as if a CE (positive) date.
- select the note and use the stamp.
I hope that helps…