First computer with real-time clock?

Regarding a message that appeared on this thread with the approximate quote: of over a minute per dat [sorry I it the delete key too quickly on the message to post the EXACT text] 1 Day = 86400 seconds * 0.01% [100 ppm] = 8.64 SECONDS per day. Not good enough for long term time keeping but much better than the previous poster indicated. I was involved in the development of som Military systems [1979-1983] that used a tempe0rature stabilized crystal with 0.5ppm stability. To the best of my knowledge this was a "state of the art" implementation of automomous time keeping for 1979. 1.0% = 0.01 = 10000ppm = 864.000 sec/day 0.1% = 0.001 = 1000ppm = 86.400 sec/day 0.01% = 0.0001 = 100ppm = 8.640 sec/day 0.001% = 0.00001 = 10ppm = 864 mS/day 0.0001% = 0.000001 = 1ppm = 86.4 ms/day 0.00001% = 0.000001 = 0.1 ppm = 8.64mS/day