On Wed, Dec 13, 2017, at 14:12, Doug McIlroy wrote: I'm not sure what you're suggesting - UTF-8 works because it's a variable length encoding - a variable length timestamp might be interesting as an academic exercise, but there's no way for time() to specify how much space is needed, or be informed of how much space is allocated Anyway, making it use an "unsigned" 32-bit value is a bit less trivial on V7 (where AIUI there's an unsigned type and a long type, but not both), but the following works - not tested on actual V7 yet, but works with the values as int16_t/int32_t on a modern system /* * break initial number into days */ hms = *tim % 86400; day = *tim / 86400; if(*tim < 0) { hms += 109696; day += 49709 + hms / 86400; hms %= 86400; } 47909 days + 109696 seconds = 2^32 seconds. The "extra day" is to ensure hms is positive. This is instead of the existing hms < 0 clause Making V6 do it (no long *or* unsigned type) is a bit more involved, but I'm close to something viable. Incidentally, one gotcha I've run into is that the code as-is passes the year minus 1900 to dysize, whereas modern dysize implementations that respect the 100 and 400 year rules require the full year. My current attempt to extend it to more bits without resorting to floating point relies on the fact that 86400=675*128 to eke out an extra seven bits without implementing a general purpose division algorithm, which gets it as far as the year ~10680 (~19391 unsigned). Though without a long for the day count, V6 can only get to 2149.