Pretty much any intercalary cycle will precess ever further off, for a naturalistic set up. It's just a question of how fast. Is it okay if it adds up to a day every hundred years? Thousand years? Fifty-thousand years?
If it's a hundred years, it shouldn't be too hard, but that seems too inaccurate to be content with, to me. If it's a thousand years, or a couple thousand years, you might have to do some judicious tweaking of the exact fractions to get something that'll work, but not too bad. Fifty-thousand years, you'll either have to do a ridiculous level of precision tweaking, or else have larger intercalary cycles.
But it does sound more like some I used for Akalet would be acceptable to you than I thought at first, which raises my estimation of possibility. It would make it whole lot more possible if you allowed for a second-level intercalary cycle, of say, 2-5 (or 11, or wahtever) 11 year cycles. Having it work out the same way as it would if they intergers is ... um.
Re: *math-related despair*
If it's a hundred years, it shouldn't be too hard, but that seems too inaccurate to be content with, to me. If it's a thousand years, or a couple thousand years, you might have to do some judicious tweaking of the exact fractions to get something that'll work, but not too bad. Fifty-thousand years, you'll either have to do a ridiculous level of precision tweaking, or else have larger intercalary cycles.
But it does sound more like some I used for Akalet would be acceptable to you than I thought at first, which raises my estimation of possibility. It would make it whole lot more possible if you allowed for a second-level intercalary cycle, of say, 2-5 (or 11, or wahtever) 11 year cycles. Having it work out the same way as it would if they intergers is ... um.