That does sound like it could be the cause.  The software version is on the label of the module according to the data sheet. The A203H data sheet also states it must be shut down 1 second before power is removed to avoid corrupting the internal flash memory,  if I read it correctly, so it is also probably a good idea to keep the clock running constantly. Andy

Some facts about "time" (as far as i know): GPS satelites have a clock which is set to "GPS time". GPS time has the same unit as UTC which is the SI-Second at sea level. So the atomic clocks in the GPS satelites in about 20.000 km height have to be adjusted to this time scale. GPS time differes from UTC by the number of leap seconds since 1.1.1980 (18 seconds until now) The GPS satelite sends the GPS time and the GPS receiver computes the UTC. For this purpose, the Almanac (send by the satelite) contains information about ionospheric data to compute the travel time of the signal and information about past and future leap seconds. The NMEA output of a GPS receiver contains only the computed UTC. For a short "Time To First Fix" (< 35 seconds for a cold start of our A2035H) there is no Almanac needed. So it would not be a surprise, if our nixie clock would be wrong on start up. The almanac needs at least 15 minutes to load, so I would expect a more precise time after let's say an hour. My clock is running wrong constantly, so most probably there is a problem in the firmware of the GPS receiver.

Thank you Ton, I got it.  

Hi, your nwatch is great. I would like to build it on my own based on your article. But I have a problem to find the right touch panel and the S1-S3 buttons. Can you please give me further information or links where you have bought these parts? Thank you very much! Matthias

Hi Mans, Unfortunatly I do not own equipment with frequencies higher than 1GHz. I posted new firmware which contains the possibility to do your own callibration when you have the equipment for it. Maybe someone else reading this and owning the equipment can help us out. joost