> which is fine, except that it's a huge administrative headache, as inflation is not constantly measured, and you will have to estimate it for periods where it's not known.
The BLS publishes the inflation numbers monthly. Higher granularity than that is negligible and hardly even measurable; the main issue is when you hold something for many years and the rate of inflation is in the double or triple digits.
Also, this stuff is already being done by computers. The computer needs the dates to determine if it's a short-term or long-term capital gain so it can use them to calculate the inflation using the official numbers.
> Simply discounting capital gains tax is sufficient as a simplification.
The difference is enormous. If you hold something for 18 months and the inflation was 6%, you get the same discount as if you hold it for 50 years and the inflation was 600%.