gain or loss on vehicle converted from personal to business use

[JGCPA]

Car was bought 8 years ago for personal use only. In year 9 the car was converted to partial business use, with standard mileage taken. Car was sold end of year 9.  Do I use the % of business miles from acquisition date or date of conversion? From other posts on this site, it seems I use % from acquisition for gain, and % of business use from date of conversion for loss. Is that correct? And for holding period, is that dependent upon same rules for gain/loss. If basis is date of acquisition, holding period starts at date of acquisition. And if basis is date of conversion, holding period starts at date of conversion?