Turns out Citizen has a crazy amount of patents on both the radio control mechanism and the eco-drive mechanism. It's insanely complex stuff - everything from where the solar cell is located, to the placement of the radio antenna within the case, is patented. Reading these patents, it's amazing how much time and energy went into this technology. Everything has been considered.
The claims are quite interesting. For example, US patent 7,372,779 is an issued US patent, with the following abstract and first claim:
The invention is directed to obtaining a radio controlled timepiece that, in a case when the user who uses it moves from one country or one region to another where the time difference is different, has simplified an operation of correcting the time difference between the countries or regions and an operation of correcting the time difference due to daylight saving time's being executed. To this end, the invention provides a radio controlled timepiece 1 that, in addition to the radio controlled timepiece 1 in the prior art, it further includes offset time difference information storage means 8 that stores an offset time difference between a country where reference time information is formed and a country where a standard radio wave has been received and daylight saving time information storage means 9 that has stored therein for future use information on whether daylight saving time is being executed in the region where the standard radio wave has been received, and local standard time information forming means 10 that, with respect to the reference time
information of the standard radio wave that has been received in a particular region, executes calculation processing by using at least either one of offset time difference information with respect to the reference time information corresponding to the particular region and daylight saving time information in the particular region, to thereby form local standard time information in the particular region.
1. A radio controlled timepiece, which comprises: a reference signal generating means that outputs a reference signal; a time keeping means that outputs time keeping nformation based upon said reference signal; a display means that displays time nformation based upon said time keeping information; and a receiving means that receives a standard radio wave having time information, whereby output time nformation output from said time keeping means can be corrected based upon a reception signal output from said receiving means, and wherein said radio controlled timepiece further comprises: an offset time difference information storage means that stores an offset time difference formed between a certain region and a particular region where said standard radio wave has been received, by setting a time information in said certain region as a standard time information; a daylight saving time information storage means that stores therein information whether or not a daylight saving time is executed in the region where said standard radio wave has been received; a local standard time information forming means that executes an operational processing by utilizing said offset time difference information formed between said time information of said standard radio wave as received in said particular region and said standard time information, and said daylight saving time information used in said particular region, so as to form said local standard time information in said particular region; and a time difference correction history information storage means that stores information on whether or not a user has manually corrected time difference information, and wherein said radio controlled timepiece is configured so that when said radio controlled timepiece has received said standard radio wave, said offset time difference of said offset time difference information storing means is adjusted by utilizing said information of said time difference correction history information storage means, said daylight saving time information stored in said daylight saving time information storage means as obtained when said standard radio wave has been received at an immediately preceding sampling period, and said daylight saving time information as obtained when said standard radio wave has been received at the present sampling period, and then said local standard time information of said local standard time information forming means is adjusted based upon said adjusted offset time information and said daylight saving time information as obtained when said standard radio wave has been received at the present sampling period.Based on the abstract, it looks like my watch is covered - the time is automatically calibrated for the time zone and daylight saving time information received. However, I'm not sure whether the watch falls under claim 1 (not sure I have a "reference signal generating means" on my watch).
US 7,408,845 seems more on point:
1. A radio correcting timepiece comprising signal receiving means for receiving plural standard radio waves having time information and timepiece means for correcting time operation to display time on the basis of the time information contained in at least one standard radio wave received by the signal receiving means, wherein: said correcting time operation operates to receive said time information according to a predetermined receiving order for each standard radio wave, and in the case of success in obtaining said time information from either of said standard radio waves or in the case of unsuccess in obtaining said time information from all of said standard radio waves operates to terminate said receiving operation, and, further in the case of said success, operates to correct the time based on the time information obtained, and, on the basis of the information related to success or unsuccess in obtaining said time information from one or plural standard radio waves obtained by said correctingBut the coolest are the design patents. US D554,536 definitely covers the design elements of my watch, though I guess you'd have to have all of the designs to be confusing... If they really wanted to cover it, they would have separate design apps for the different "portions" of the design - the slide rule, the face, the hands, etc.:
time operation operated in the past, said predetermined receiving order of each standard radio wave used in said correcting time operation after the past time is renewed.
It's kind of cool. And Citizen, (or Swatchgroup, or anyone else) - if you're looking for someone to file your industrial designs in Canada, let me know - no one else will be able to convince the Canadian Patent Office of the distinguishing elements of your design better than me!